Windows 7 has been extremely stable in our tests. Our benchmarks have it going faster than a MacBook and even faster than Windows XP. We've had the discussion of PC versus Mac before, but no matter what, you'll eventually wind up with a program that you wish would run, but can't because it's a Mac.
I use them both daily and they're both fine machines, but PCs are not only cheaper, they're still the market leader and most software is written for them. Sure, I do IT stuff as a career, but I've never had a virus before. It's really just about being cautious where you browse.
Stay off those porn sites.