Won't slow your Mac down if you use Bootcamp, Windows installs on a partition on the slower 50% of the boot hard drive from the bottom up, however that shouldn't affect PC game performance all that much, only when loading data it might not be as fast as it can be. Likely hardly noticable really.
A Mac actually makes a remarkably solid Windows computer, and while it's not designed specifically for gaming, most models' discrete graphics make them pretty good for the task.
OS X might feel a bit more snappy as it loads from the faster top 50% of the boot drive.
If you have a SSD then it doesn't matter about the drive performance.
Outside of that Windows will run on the CPU and dedicated video card just about the same, as since OS X and Windows are in seperate parittons they boot seperatly and thus have full control of the hardware.
Now if you also install virtual machine software like Parallels or VMFusion that can copy the BootCamp partiton to use Windows in a window in OS X, and you run other programs in OS X and Windows/programs at the same time, that could slow down your Mac as it's running two operating systems and several programs at the same time.
A powerful Mac, a recent 15' or better should have no problem, as long as there is 4GB of RAM or more. However for best 3D game performance it's better to direct boot into Bootcamp to let Window shave full hardware control and Direct X drives.
Virtual machine software uses the OS X OpenGl drivers, so any program in there will have to use Open GL drivers.
The 13' is better off using Bootcamp and direct booting, it won't be good at games anyway as it doesn't have a more powerful dedicated video card.
Ideally Windows 3D games should be played on a dedicated Windows 3D gaming tower, this way the video cards can be exchanged for newer ones which on the Mac you can't.
If you intent ot Windows #3D game, go that route and don't bother with gaming on a Mac as you can't upgrade the hardware. (or get video cards for the MacPro if sticks around, it hasn't been updated in ages)
Jul 27, 2012 8:27 AM