Don't use a mac if you want to get into using lots of different programs... Especially a lot of modelling programs are not compatible and you're gonna have issues transferring your files/converting files alot! I use lots of different modelling, drawing, audio and game engine programs, and lots of them fuck up with apple, speaking from my own experience.
If you just stick with designing (graphics), then a mac is perfect, but modelling I wouldn't recommend it.
If you get a laptop, i recommend lenovo, if you are going for a desktop PC, then get one with enough RAM (4-8gig) and standalone videocard (not integrated!) to support those programs, as they're gonna need that!