Gearing is a funny thing..... If there is a particular aspect you are trying to improve..... steady state driving, rolling hills, climbing mountains....
Shorter gears usually help by bringing RPM up, it can also put you in between gears when climbing. If you have a good gear for climbing (say 2nd), and a good gear for cruising, (say 3rd), remember, if you go shorter, you climbing speed could drop in 2nd, and 3rd may still be too tall. Same with cruising, shorten 3rd, 4th may be too tall, now you are 300 - 400 rpms higher at the same speed.
Here's and example....My truck has the 3.73's, but with say 3.55's, I'd have better climbing speed in 2nd, the truck would pull a little more rpm in 4th, making it less prone to downshifts, (I now run 5th, barely), and better unloaded mileage.
Just a thought....