PoE is fantastic. The atmosphere and difficulty is perfect for a game like that and the currency system in that game is equally terrific. It starts slow and unimpressive but it builds and eventually the spell effects and combat become a lot more flamboyant. D3 looks great but that is where it ends. The currency is uninspired and starting a character and hitting up the ah to gear up is just not fun. In PoE I actually find upgrades and if I get an item with good base stats I can scrub it and use an orb to make it rare use another item to give it sockets another to link them and another to change the rare stats. Sure I might end up with a fail item but it sure is fun chancing it. In D3 it's ah or nothin.
Another thing is that the community in PoE is really great with plenty of chat and trading. In Diablo you never see global chat and there is no trading because what's the point when there is an ah. D3 is just a cold soulless game imo.