It's just that WoW was a less "cobbled" game to start with, so not as much difference.
The cool parts are of course the "Rifts" which are continual/ongoing invasion portals that open up all around the world. It's basically "pick up raids" for those who hate committing to a 60-person Raid that takes a few hours to get through; if you run across one, you have the option to simply join the public group and get assigned to a team, you fight, then you go your way. It's pretty cool.
The 3-soul system of skill tree building (where you mix and match whatever trees you want, hopefully to build synergy and reflect personal play style) is pretty cool too.