I’ve been playing Path of Exile for a while now, and I think there’s some design differences that are worth discussing - one is not necessarily better than the other, and I think it’s very clear that some philosophies are very different.
Trading and Economy
The biggest and most obvious difference between Diablo III and Path of Exile is their approaches to trading and the economy in general.
Diablo III launched originally with an Auction House to allow players to quickly and easily put up to 10 items for sale, and then eventually added the ability to buy and sell items for real money as well. This system was met with much disdain, as players perceived that good item drops were made more difficult to acquire (than they would normally be without an Auction House.)
It then switched gears completely with the release of Reaper of Souls - Reaper of Souls essentially made every player have to find their own gear as gearing became moved to set items and legendaries (instead of rares or yellows) or whatever the group found while playing together. (In Path of Exile, this is known as SSF - Solo Self Found, which is essentially the mode where you make the conscious mode not to participate in the economy.)
Path of Exile has trading, but trading is made more difficult by requiring players to manually message each other and negotiate in order to complete trades. The developers, Grinding Gear Games, have made it clear that their philosophy is that trade should not be easy. Recently however, their position is probably being slightly challenged by the fact that currency bots are now dominating the currency trading market. This, in addition to constant community feedback that the market is too easily manipulated by people who are putting up price listings without a genuine desire to sell, may make eventually force their hand. It remains to be seen whether this will change in the future.
I am honestly very fond of trading. Even with the additional friction of having the message multiple people at times to get the item you want, it makes it very accessible to get specific pieces of gear as well as get currency to enable you to either craft or buy items that you need for your build. It is a shame that Diablo III no longer allows trading, but their solo self found philosophy has its merits - I know that all my gear is mostly earned myself and I get the benefit of playing the item slot machine myself, as opposed to Path of Exile, where it is often grinding out sufficient currency before being able to participate in the excitement of getting your own gear.
Diablo III, with the introduction of Adventure Mode has allowed many options for levelling characters - you can play through the campaign, do bounties and rift in Adventure Mode, or alternatively, you can be power levelled by someone in a rift. Endgame begins the moment you hit level 70, it doesn’t matter how you get there.
Path of Exile has a much more opinionated approach - it forces you to play through the ten acts of its campaign before it allows you to even think about entering the endgame - Maps. Recently in Delve league, it has become possible to power level someone via low-level Delves (and having a lot of fuel.) However, as this system is changing in the next league, being Betrayal, it remains to be seen if this will be changing. (You will still need to kill the final boss to access maps, however.)
My preference is, of course, strongly for the ability to power level and play however you want - this suits me better as I have limited time to play, and can’t afford to spend 8 hours of more of my limited game time to level a new character.
Diablo III has a very simple build system - you gain skills as you level up for the class you have chosen, and if you enable Elective Mode, you can use any combination of 6 skills you want - usually this is in tandem with the set items you have. If you want to play a different build, all you have to do is find a new set of items that works for that build - then you can just click over and switch all your skills over.
Path of Exile has a much more complex system - a build consists of the class you’ve chosen, the subclass (Ascendancy) you’ve chosen, your passive skill tree pathing and the skill gems that you have. There are some builds which depend on having certain specific or unique items, but often these are either optional, or stepping stones on which before you advanced to much more powerful. I feel Path of Exile’s passive skill tree is definitely overly complex for what it does. It also makes your choices feel less impactful, as every point you put into the tree does very little by itself, although as a whole they stack up into a useful total.
Diablo III is clearly built to be more friendly to the casual player - there is very little customisation that you perform on your specific character, but on the other hand, you don’t have to keep creating new characters if it so happens that the skill you are building around requires a completely different setup (with the exception of being in a different class.) If you want to switch play styles from a Marauder Demon Hunter to an Unhallowed Essence build, you aren’t going through another 4 to 8 hour slog through story mode. On the other hand, every single person’s Marauder build is going to feel and play nearly the same. However, that’s not to say Path of Exile players will behave differently - there are still “meta” builds and you will often run into very identical looking builds while playing with others. (Poet’s Pen Inpulsa Elementalist anyone?)
The constant Path of Exile updates however, negate the feeling of all builds feeling the same - you can very often find something new to play, even if it may be slightly less efficient than the fastest or best build. I believe this is why Path of Exile is generally viewed to be the better game - it’s just updated more frequently. If Diablo III had updates at the same place, I’m sure it would be in a similar place as well. (Imagine a world where we constantly got new set items, new skills and new legendaries!)
Diablo III’s itemisation is definitely among the more disliked aspects of it - it hasn’t changed all that much since the original release. Smart Loot has made it behave much better, but it still follows the same basic tenets: you want Crit Chance and Crit Damage wherever you can get it (except for some builds which prioritised Cooldown Reduction) followed by as much main stat (Strength, Dexterity or Intelligence) as you can get. It is extremely simple to grasp - and it doesn't feel like you'll easily be lost in depth and complexity - you can very quickly get a grasp of what's best of your
Path of Exile’s itemisation appears to be better, but really it’s the same as when Diablo III’s original launch. Stats are random, there is no smart loot. However, you can trade for better items, but that’s something we will discuss later. As you get a lot of damage from your passive tree, your items are often confined to survival-oriented stats. Besides your build-enabling items or uniques, you are often chasing life and damage resistances. After that, then you begin to hunt down damage boosting items. There is definitely a better variety of damage boosting affixes, as different builds function differently from the code point of view, and therefore scale differently with different affixes. This is definitely deeper than just focusing on main stat, but the systems here are often far too opaque for my tastes and require too much research. For example, flat physical damage is highly desired for conversion builds over flat elemental damage due to it scaling better. “More” damage mods are better than “increased” damage mods, as “more” mods are more difficult to get than “increased” mods, which are abundant on your passive tree - so the rarer “more” mod generally gives you more damage per %.
Diablo III really has very little crafting - you are either building a ready-made recipe from Haedrig, the blacksmith or you can gambling via the Kanai Cube. It's really not something you even think about in Diablo III. (There's augmentation, but can you really consider it crafting?)
Path of Exile really shines from an itemisation point of view due to crafting. While mods are random, they are constantly adding new and exciting ways to gamble currency on building amazing items, along with many ways to improve your chances of crafting your “dream” item. While a lot of aspects of crafting are random, many are not - Path of Exile’s crafting options go extremely deep. Especially with Delve’s crafting mechanics being added into the game as a core mechanic, you can now pretty much guarantee yourself a good chance of getting an item you can use if you go in with enough currency. (Mirror-level items, of course, require multiple mirrors of currency to craft, usually.)
Crafting mostly serves as an item sink - in this respect, I believe it is very difficult to top Path of Exile - the crafting options are numerous, the tactics and strategies for crafting items run deep and are overall, extremely fun to engage with during the overall item chase. However, it needs to be noted - this is hardly the core gameplay loop and it is completely understandable that this is not fun for a good percentage of Path of Exile players, who may choose to grind for currency instead. In Diablo III, you can only get items by running through more of the core loops.
Diablo III has pretty much two choices for the endgame: Nephalem Rifts and Greater Rifts. You run Nephalem Rifts for gear and Greater Rifts for experience points (as well as levelling gems and augments.) Besides that, you don’t have much choice. It’s very simple, but I find it works very well - it’s a very quick way to immediately engage in the core gameplay loop: killing monsters.
Path of Exile definitely has more choice of the endgame. You can choosing to kill bosses - some of which are so hard a good percentage of the player base have never attempted them. You can choose to farm the Eternal Labyrinth (although I believe most people see this more as a transition phase.) You can also choose to not kill anything and work on trading and crafting instead - a perfectly viable option. However, if your intention is to kill monsters like most of the player base, you run maps. Maps are essentially like Nephalem Rifts, but you get to pick the tile set instead of it being completely random. You also get to craft maps - you can roll it with the desired mods, and you can also add certain properties using the “Map Device” to do things like add previous league mechanics, reroll the tile set that your map is on and so on. The options here are endless.
The endgame is really the meat of both games - it is where you will end up spending the most time playing, so it is extremely important. I prefer Diablo III’s Nephalem Rifts significantly - it is a much simpler system. I choose a difficulty, then I can just mindlessly kill monsters and pick up loot. Then, I switch to Greater Rifts to progress my gem levels and Paragon levels.
That’s not to say that Path of Exile’s endgame is bad - it’s just too much mandatory micromanagement. Path of Exile has map progression where you slowly work your way through the 16 tiers of maps as well as some unique maps. However, this system is complex and often frustrating. You often run into situations where it feels like you are running out of the maps at the tier you wish to run. You can’t always just put in a random map and run, as it could slow your Atlas (where your map progression is tracked) progress significantly. Before you run every map, you need to craft it and then check that it doesn’t have affixes that could be deadly to your specific build. On top of this, you may also have to choose a mod from the Map Device to stack on top to improve your map returns. (And while you are doing this, you are also organising hundreds of tiny Map items in your inventory and stash.)
All this very quickly stacks up to cost you hours in just micromanaging your tiny little Maps where you want to get back fairly quickly to the core gameplay loop. Some of this is in line with the developer’s philosophy - they want the game to be hard and they don’t want players to just play through it mindlessly.
This has been a fairly extensive rant, so let’s summarise my opinions:
Path of Exile’s crafting, trading and economy are amazing compared to Diablo III.
Builds and levelling is honestly a toss up - there are things I like about both.
Itemisation is a philosophical split - you either prefer the simpler approach Diablo III has taken, or you prefer the deeper options provided by Path of Exile.
Diablo III has a simpler rifting endgame that I believe Path of Exile could take some lessons from.
Overall, Path of Exile definitely demands more from the player compared to Diablo III, whether it comes to thinking about builds, time commitment, crafting or the endgame. That’s not to say it’s a difficult game - but you shouldn’t go in with the expectation that you will see everything. You should go in with the expectation that you will need to put effort towards seeing everything - and it will be rewarding.