The real question is what do you intend to do (For example, AutoCAD and
WYSIWYG only run on a windows OS, wheras
Qlab only runs on a
Mac), and what you are more comfortable with. I run a
mac because thats what I have always used, so I am much more comfortable with the OS. One plus for an Apple product would be that you can dual boot it with windows and OSX on the same machine, which might be more useful to you. I currently have my MacBook running OSX 10.5.8 and Windows XP with whatever the latest SP was. As soon as I can afford it, I am going to ditch that partition and get myself a ThinkPad or HP or something that makes sense, to use
WYG on. If you intend to do a lot of 3D work and not go to tons of gigs with the computer, your probably best off getting a desktop of some sort, because you can toss a TON more
power under the hood, and you will want some hard core graphics capabilities. However, once you do this, you wont have the option of going to the gig and using the computer for stuff while there. Decide what you need to do, and then figure out your price range, and then figure out what fits best. Also, if your going to a lot of gigs with your machine, youll want to maybe double backup the entire
system (one in the gig bag, one at home, maybe one online) and get a less-expensive machine because the chance of it getting damaged is fairly high.