Depends, if you're doing a graphics course or something then I guess a powerful desktop would be cheaper than a equivalent laptop. That or if you game a lot on your PC then a desktop would be the obvious choice and a cheapy laptop/netbook for taking notes I suppose.
My laptop is fine, it plays most games on low/med settings and plus its light enough to lug around places. :P
Have a gander at that. Pretty decent laptop, capable of running BF3 with playable FPS at medium settings for £539, not a bad deal. You can get one with an i7 in for an extra 100. I'm probably getting it for Uni.