Windows baby! why? because is just that....software. They don't try to dominate every aspect of computing including hardware like Apple.
Hence the great variety of applications and the inherently open nature of Windows
You can bitch all you want about crappy performance, crashing, and viruses but that all boils down to poor hardware, unstable applications and user error.
Besides, the rest of us don't need to wear turtlenecks and use round white blocks to feel good about ourselves.
Oh, and vista loads in about a minute for me, if you can't wait that long then maybe you need to rethink some things.
EDIT: forgot to mention, if you really must have your system ready instantly then instead of turning off your computer, just put it into auto sleep mode. It saves energy and opens instantly.