Where WoW is a PVE game first and PVP game second, WH is the opposite. WH's PVP is far superior. WoW's PVE is far superior. Depends on what you like most.

I like PVE better so I still play WoW.

Also, you gotta have a pretty hefty box to run WH. Its graphics are a lot better than WoW.

As for me, I got Lich King on reserve.