@DCCCXIX honestly I personally don't really care. The main difference for me is that every aspect of the current game is so unpersonal. Crossrealm dungeons and raids have realy destroyed the game for me. Nobody is realy talking in the chat anymore the current game is pretty much dead.
In Vanilla you have to communicate to create a group to go to dungeons.....I don't want to start with organizing 40 ppl raids. People have to get themselves together. If you are verbally abuse ppl and leaving the groups you are an outcast on the sever. So for me this a big diffference maker in how to play/approach the game.
Also to name a few things which I realy miss:
Bigger talent tree for creating hybrid classes again
Different levels of one spell which makes healing for me far more interesting
Manamanagement 5 sec rule old time thing
Actually seeing people in the open world more often
Seperate auction house (Booty Bay welcome back!)
Just to name a few