I've always enjoyed playing console games more (with the exception of Counter-Strike) so I am going to go with my 360 rather than my PC. I can sit on a couch when I play the 360 version. For the PC I gotta sit on a chair and since I plan on playing this for hours on end when it comes out, I really gotta think about which set-up is more comfortable for me to use.
The 360 version will likely have more people playing online at any given time. The PS3 may look better but I still don't think there are many 3rd party games on the PS3 that actually do look better than their 360 counterparts. Developers often cite the immense difficulty behind developing for the PS3 as a reason for this.
Also, I already own a 360. At this point there is just more to things you can do with it than with a PS3 (Xbox Live + game selection). So, yeah, I guess I got no choice than to go with the Xbox for this one.