I all honesty, I prefer D3 over D4. I find the D3 art style much better than D4s. Yes, D4 is miles ahead regarding textures, details and resolution. But the style itself is pretty boring. Mostly mud, dust and fire.

And concerning the gameplay, I played a sorc to level 60 and a rogue to level 20. And playing them feels like work while playing D3 you feel powerful.