regearing doesn't = more power. In first gear, it will make some difference. If first gear used to top out at 80MPH and now tops at 60MPH. Yes it will have more pull.
However, If you gear your bike where your third gear tops at 100 and a stock gearing second tops at 100. you'll be in third thinking, "man this third gear pulls hard." and the stock guy will be in second pulling just as hard.
Regearing will give you a little going down the starights only because when you redline 2nd gear and shift to third, a regeared bike will drop to like 12k RPM when you get into third, while a stock geared bike would drop to like 11k RPM. But you'll never notice the difference.
I gear for the corners. If I apex the corner in 2nd at 13.k RPM or 3rd at 9K RPM. I'm between gears for that corner. I'll change wehre either I'll apex in 2nd. at like 11k or 3rd at 11k. I just don't want to shift just coming out of a corner but I want to stay in the power too. That's why I change gearing.