The great thing about D3 vs WoW is that you can fully enjoy D3 solo or with a group. In WoW if you are a hardcore raider you will likely eventually find that you have nothing to do outside of raiding. During every tier that I raided I would eventually get to a point where there was simply no benefit to playing WoW outside of raid, and much of that was because I found the character mechanics/abilities of WoW boring.