I'd choose Windows. OS X is slow and software support is inadequate. OS X GUI design is just a horror.
Btw at local university students can choose to use OS X, MacOS 8 (yuck! terror!) or Windows XP. I don't know why but Window XP machines are always populated, few activists are using MacOS 8 (!) and OS X machines stay unused. You can even print for free from Macs (from XP it costs 5 cents per page) but Macs are still mostly unused... There are also few Linux machines for email reading via Pine. They are almost always occupied, too.
