The difference in price is $200, and the primary differences between the two is that the more expensive have 30 bit color depth (against 24-bit) and a 6ms lag (vs 8 ms lag). There's other things on the more expensive monitor, like PIP, media card reader, and more USB ports, but i'm not too concerned about that.
I'll be gaming, but I'm not pro enough to take advantage of a 2ms lag difference, I don't think.
So to me it comes down to colors. I can understand why someone who edits images or videos would need a billion colors, but is it going to make a difference for a gaming experience? Can the game take advantage of a gradient that fine? Can my gtx 560 make use of such a gradient?
You generally need a workstation (professional) graphics card to make use of a LUT table. The 2ms difference in response time should not be a big deal, beside response times are not an exact science and in many ways a marketing ploy.