If you have more than a little experience with both Windows and Mac OS X, chances are very high (just short of 100%) that you prefer Macs. That's not to say that Macs are perfect; if they were there'd be no need for the frequent updates to their system software and basic applications. What they are is better, clearly better, unmistakably, unequivocally better than Windows, for practically every purpose, in very nearly every context...and getting even better faster than Windows. (Many have taken the position that Vista is actually a step backward.)
Compare Mac OS X 10.5.2 and Windows Vista on equivalent hardware, and you'll be blown away by how much more responsive the Mac is, no contest, no kidding, no room for debate. Comparing the interfaces is more subjective, and people tend to prefer what they're accustomed to, but people who've made the transition from Windows to Macs commonly say they'll never go back. Counter examples are about as common as hen's teeth.
The game isn't over, of course. Windows still enjoys huge market share, but it's becoming increasingly difficult to find any reason for this aside form momentum and habit. There continues to be some remote chance that Microsoft might pull a miracle out of its hat before that market share drops below 50%, but don't count on it; Microsoft itself certainly isn't. They're moving quickly to get into other businesses besides traditional personal computing.