Funny enough the 640 gig black is slower then the 1000gig blue.
Greens are mostly for power savings. I use one for my backup since it was cheap/large/quiet/cool
I had 3 blacks(i was kind of surprises, they are fairly quiet too) in (r)aid0(no redundancy in mode 0) and it was good and fast until one started to die. This is how i got the 1000gig blue(its what WDC sent me). I just rebuilt with 2 and moved on.
For Starcraft 2, you are limited to other players anyway. It makes you wait until everyone is loaded. From that point on the game should run from computer and video memory and not have any use for the hard drive.
If you want a faster SC2 game, its all about the cpu. Overclock it