OEM usually contains the O/S only, where'as retail has extras and costs more.
Most people that I know, save the money and buy the OEM version.
As far as gaming is concerned, there is no difference in gaming as far as I know, however, I have noticed written information on some game packs (new games), stating that the game will work with Home but not Pro.
<font color=red>DCB</font color=red><font color=white>_</font color=white><font color=blue>AU</font color=blue>