well I played EQ for almost 3 years. I know about it's addictiveness, it's time sinks, and how Verant controls every aspect of the game, regardless in many cases to the wishes of the Player.
I also have tried Star Wars Galaxies, Verant/Sony's other MMORPG. I did so at release, and then again just this past weekend. Simply put, it's worse that EQ. I love SW, but that game is unplayable. The amount of time required to succeed in SWG is so much worse than EQ it's amazing. I played EQ 30 to 40 hours a week, and still only made it to level 51 after almost 3 years. I probably would have kept playing but my family added 2 girls in that time, and as they reached 2 and 3, it became apparent the I had to choose one or the other, and EQ lost of course.
SWG seems no different, and I would not expect Verant/Sony to change the formula much. They will want it to take years to reach the end.
As for WoW, I was able to try to stress test a couple of weeks ago. Ran beautifully. I loved the interface, how easy it is to spot an NPC you need to talk to (big huge yellow ! mark over their head, or a ? mark depending on if you are completing a quest or they have one ot offer). Fighting was easy enough, and at the early stages, you weren't expected to die from measly rats and snakes and bats hehe
As a more casual gamer now, I'd say WoW is for me. I'm actually considering it. Though the biggest hang up I have with any of the mmorpgs is the need to be on constantly to stay in touch with the friends you make and keep leveling together.
I've also played DAoC, Anarchy online, Eve, and City of Hereos, so I'm familiar with the issues they all have. I have to give Blizzard credit, the short test I had makes WoW look like the most polished, from an ease of learning perspective, and seems to be the only one not designed to make the player go to the web constantly looking for help and guides. That's nice for me.
I say all this because you might not have the same interests. But you should understand from whence my opinions come so you can make your own appropriately
I'm willing to bet they'll both be huge hits