This one really depends on how you will be using this system. If you are doing any kind of multimedia work, you should be looking at Apple. If its just basic home or office use, email, facebook, surfing, posting at physics forums, working on documents and presentations, then Linux distro like Ubuntu is a very good choice. If youare going to do basic home/office use + gaming then you want windows. Ubuntu can play games built for windows through WINE but it can be flakey.
I have a philosophical disagreement with apple, they want to maintain control over hardware you buy from them while I want control over hardware I own. Take the new macbook for example, the ram is soddered on, a proprietary solid state drive, etc. The idea is to prevent you from changing the configuration, getting upgrades from anywhere else than them. If the memory fails, i can't go to the local computer store, spend 30 bucks and buy more ram, no i have to replace the motherboard that's only available through apple.
This forces me to get apple's iCare or i will pay through the nose if something fails. When i purchase a computer, its mine and i want to do with it whatever i want, change whatever i want. Stuff like this really irks me, that's the biggest reason I won't get an apple product even if its better, i don't support what they stand for.
Microsoft is also like them but they arent a hardware manufacturer so its just not as blunt or extreme so the lesser of the two evils. I always try to do what I want to do in the Linux environment first, if I cant, I'll tuck my tail between my legs and use Windows.