WoW is just a bit dated on the graphics, thats all. I hope wotlk improves the visuals (as much possible since it's not a new engine).
... and there must be a reason people are addicted to WoW don't you think? Why not addicted to something else?
From what I have seen they have just added realtime shadowing in WoTLK, I think any other "improved" visuals are just more attention to detail given by the zone designers.
On getting AoC, I would truely recommend getting hold of a buddy key or waiting for a trial... I loved AoC when it was released, but several patches later and my account is cancelled and i'm going back to WoW. Funcom utterly changed the core gameplay (for the worse) in mini-patches a mere few weeks from release... if they are that insecure about their own game then I don't hold any hope for it at all.