Well its hard to help you decide which one when we don't know what the intended purpose is.
For gaming, currently a MacBook (Pro) (running OS X or Windows) isn't necessarily the best as Apple only update the graphics card every one to two years. When they do, they typically use the latest and greatest (within reason) so buy a MacBook (Pro) soon after a refresh. Outside of a refresh cycle, try a non-mac laptop.
For general web browsing/email/etc, a macbook (even the NetBook Air) would be over powered so the best solution would probably be a large screened netbook.
For any development, I would suggest a MacBook. Why? OS X. In my opinion, OS X is the best platform to develop on: it being UNIX-Like and a Commercial OS with good commercial application support; and a well-thought-out development flow; it just makes development much smoother. Try getting GNU GCC working on windows or Photoshop on linux (Cygwin, Wine need not apply).