Depends on what you want to do, and macs tend to be extremely expensive and overrated fo their preformance.
I am currently using Vista on my gaming desktop, and dual-booting Vista and Ubuntu on my laptop.
Macs are more ntertainment oriented and they are hard to customise from personal expence. While on a PC you can do a lot of custom work to it, depending on what your level of tech knowledge is you could try ubuntu, or another version of linux.
Long story short:
Mac = Enertainment, expensive.
PC = Gaming, business, usually better supported all around.
Linux = Anything, less supported, open source, suggested for advance users.
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