Quite frankly the best thing in Deadfire for me is the combat polish that is so sorely lacking in PoE. In PoE you can Paralyze a stack of enemies, only to find out that one of their strikes, be it a crit or a Prone has come through AFTER you've Paralyzed them. These details are in combat only, though. Despite, I am not altogether liking combat in Deadfire. It becomes too overwrought with details and back and forth balances/nerfs/patches. There almost hasn't been a single game update where they touched something and didn't screw something else, as well.
Combat in Deadfire feels a bit cumbersome, segmented and heavy and classes have lost a bit of their single player identity, because the game pursues balancing system more akin to an online game--a given class absolutely needs to be viable in any situation, albeit Chanters clearly have advantages over everything else in this regard.
In contrast combat in PoE is quick and decisive. You don't need so much beating around the bush and you can be effective while minding less details. Statuses are deadlier and more meaningful and a successful two handed attack leaves enemies well chunked.
PoE is more subtle in it's world building. The gods feel distant, mysterious and powerful. There's generally a bit more attention to detail--Twin Elms and the cultures residing within are generally better than Neketaka. That is not to say that Deadfire doesn't have good artistic qualities. Some of the characters, like Onekaza and Aruihi are very well done, but the whole feel that Deadfire gives me is more granular than PoE.
The 2d design of the game is not that better than PoE, which still looks quite good. We've gotten a lot of new and improved visual effects in the 3d, but a lot of people have mentioned performance cost.
Combat polish is the best bit, and the jerky world presentation, story pacing and lack of subtlety are the worst for me in Deadfire.