the answer to your Q is the revs will increase slightly,with the higher ratio combination. but the adv is that if your car has a increased cam profile, you'll find that you wont have to rev as much to pick up the next gear...it will be on cam earlier. In my 510 i changed from a 3.45:1 to 4;1 and the increase was phenomenal in accelleration terms. But if your after lower evs for the freeway then the lower the ratio the lower the revs..
Mark