I'm gonna play devil's advocate on this one and pick the PC over the Mac. Why? Because it's such a pain in the ass to find compatible software. If I'm about to download or buy a program, I have to check to see if it's Mac-compatible first. It's like the vegetarian of the computer world.

Also, I mainly use my PC for gaming and video editing, and it's even more of a pain in the ass to find Mac-compatible games.

Not to mention the fact that the only good Mac-compatible torrent client is Azureus, which I hate.