This post is not meant to be offensive or flaming, it's just my opinion on the subject.
Other operating systems are mostly void in this discussion. A casual gamer does not care for the *nix systems. Those however, are godsend for my programmers, and I know this since half my family works in computer programming. However, as I said earlier, I assume that the topic creator is buying merely for games and recreation. Thusly, it is MS vs. Mac.
Yes, I suppose "PC"s are more versatile (I use quotes, seeing as a Mac is a "personal computer" as well), but no one really wants to run more than one OS, unless they are programmers which I alreay covered.
In all, Macs are nice all-around packages, but of course you can do better with a specialized machine but towards your needs in a computer. Personally, I love the Mac laptops, and that's why I have one. I would rarely pick a Mac desktop model over a "PC" desktop though. I would miss the hardware flexibility.
Lastly, Macs have gotten a lot better over the last 3-5 years, so a lot of old prejudices are not warranted anymore. BTW, you can now use right-click mouses with them.
So back on-topic: What are you buying a computer for? If just to game, you're better off with a Windows-running desktop model with all those crazy packages they have now with the intense graphics cards and 500GBs or whatever is the rage now. If you don't mind sacrificing some gaming options for some nifty applications (which I admit, there are probably similar applications for Windows...) and all around more compact and clean OS, then give Mac a shot. Too bad computers arent like cars which you can lease if you really can't make up your mind at first...