So I installed this on my Windows and OS X side last night and ran about 30 minutes of game play on each side.
The Windows side was a bit more superior in terms of scaling and graphics smoothness. But I had no game crashes in OS X which is good; at least it was stable. Although, the game did load faster in OS X because of the SSD compared to the spinner drive that Windows is on, which is what I'd expect. Overall both versions look very similar, however I think the Windows version bests the OS X just a bit. I didn't measure FPS but I'm sure it's at a higher frame rate in Windows.
This was on my z68x-UDH3-B3 build with an i5-2500K CPU and a ENGTX 470 GPU.