I used to do bootcamp and while the game itself seemed to run a bit better, the lack of good support from bootcamp to support the trackpad really annoyed me. If you are going to play with an external kb/mouse, bootcamp might be the better option.

I picked up the mac license when it was on sale a bit ago and was pleasantly surprised. The game seems to run well enough for most content, even in really populated areas. Occasionally it would have some graphics glitching, but it only seemed to be if something loaded improperly. Teleporting to another zone and back would fix it. Very rarely would it crash entirely, but on that note my windows copy on my desktop PC crashes to.

If you have the extra money and like the convenience of not having to switch partitions, and also plan to use the native trackpad, I would suggest the mac version. If you want very slightly higher graphics and marginally less crashing as well as using an external mouse, I would suggest boot camp. Since buying the mac version, I have not used my bootcamp version. Bootcamp can also be a data hog if you have limited space on your harddrive.