which 2010? and the $999 sale is it the 13"? If it is, the 13" its not a gaming machine at all. It would do games from 2008 and below fine to great. but newer games would struggle a bit. SC2 has no problems though.
If gaming in OS X, the 2011 model may be a better choice for you considering that it has a faster processor. The difference between the 320M and HD 3000 is negligible in Mac OS X, but considerable in Windows.