Well, I'm not sure what gray to gray is but the shorter the response time (2ms compared to 5ms), the quicker the response you will get from your LCD, so get the 2ms LCD monitor.
Yea but according to some google searching I have done GTG is a faster process than bwb (normal) so it yields a quicker response rating. They do this to make the LCD's appear faster than they really are. I'm looking for how fast 2ms GTG would be in relation to a BWB test.