For what it's worth, my opinion follows on certain matters...;)
OpenGL support in OS X is around a full generation behind D3d support in Windows--nothing at all that Larian can do about that except use workarounds that often cause "slowdowns," at least in relation to Windows D3d performance. Windows OpenGL support is ~4.x in terms of feature support--OS X is still struggling at the OpenGL 3.x level in terms of ogl API feature support. Game support inside OS X has always been an absolute bottom-tier priority at Apple. If not for Valve's efforts, in fact, OS X would still be running somewhere on the OpenGL 2.x Windows API level. Apple's just not into gaming, never has been--has never supported anything analogous to Windows' Direct3d API & development tools.
In Windows, OpenGL 4.2 is roughly analogous to D3d10/11; OpenGL 3.2 is roughly analogous to D3d9 support. According to the last thing I read on the subject from Valve, OS X is somewhere around the Windows' OpenGL API 3.x level of support.
Best plan: don't buy a Mac for gaming, imo. Second, if you're really into gaming, then stay away from laptops--either Windows' or OS X driven! You will definitely find gaming much more enjoyable with a desktop.
But if you already *have* a Mac, you might do better with Bootcamp since Windows runs as natively on a Mac as OS X, but then you are reduced to depending on Apple to supply your Windows drivers--and Apple's never been very good with its hardware drivers, either, imo...;) Indeed, inside OS X Apple goes to great lengths to hide OS X hardware driver access from its users, whereas Windows exposes it for easy user access and configuration. (Big difference in overall philosophies between the companies...) I once had a somewhat alarming conversation with an OS X user who had somehow become convinced that OS X had no device drivers for its hardware(!)--that "hardware drivers" were only a "Windows'" thing...;) Heh! True story...(can't make this stuff up!)
