I'm just going to add to this. Games ported to Mac from Windows more often than not run like crap. The reason why is that game developers make a game optimized for Windows then later come back and rewrite the code with typically a much smaller team for Mac, this decreases the amount of time that the developers can use for code optimizations and testing. Basically bet it all on Windows, do what we can for Mac but don't count on profits from that group. Likewise, games made for iOS ported to Windows and Android run like crap unless they are optimized for the platform.
You really can't compare Tomb Raider or Bioshock because those were Windows first games, of course they are going to have great performance on Windows compared to Mac.
I'm not saying that a game can't have great performance on both platforms, I'm saying most developers pick a platform for their cash cow and then when people ask for a game on another platform they don't want to support they give it a quick glance over and say "here you go. You asked for it but we don't care enough about <insert platform> to make it great."
I honestly don't care what platform you praise, that's not why I'm chiming in, I'm just stating that if you take a single game by an age old Windows developer and try to compare it to their version for Mac, yeah it's going to suffer, what's your point?
If your arguing about what platform to play games on, as a die hard Mac fan, I'll tell you get a Windows computer. It is a better investment for your entertainment needs to spend $3,000 on a custom built Windows PC than it is the same $3000 spent on a top of the line Mac.
Mac's are great for journaling, music production, photo editing, and graphic design.
Windows computers are good for business compatibility and gaming.
Linux is good for going cheap and having a great server.
The big problem I see in most threads is that people tend to choose a computer based off the imagined status that comes with the computer rather than the functionality they need from it.