I have found that the double digit, 10.xx +, drivers are significantly faster than the single digit drivers. With my Geforce256 SDR, 14.10 is fastest for me but all the double digit ones are very close. The official drivers, 12.41, might be a tad slower than the others.
My MX400 works the best using the 12:20 drivers. Anything after slows it down with stability problems and anything before I tried had a problem with my monitor detection. So I am just sticking with the 12:20s.