Originally Posted by Mike Benvo
Because it holds power or makes more power there. Which means you're making more HP when the other car has to shift, and then you're already higher up in the band because you shifted at a higher point to begin with.
Not going to make a big difference in 1st, 2nd, or even 3rd really.. but 4th - 6th gears you could have a noticeable difference during a race just from that advantage alone. The more time you spend in that particular area due to gearing the more you're going to realize the advantage it affords you.
Another advantage is on the track when you're full throttle and need that extra couple hundred RPM. Happens to me sometimes when an up-shift isn't really feasible and you don't want to sit at the limiter when you could have a little more room there without shifting.
Another advantage is if you swap out your stock 3.15 FD diff (DCT) for a 3.62 FD diff