Do you have 3.91's now? If you do then pardon this part of this post... at 60 mph your rpms are 3031 with 26 inch tall tires. If you had 4.33's your rpm's would go up to 3360 at 60. So about 350 rpm's or so difference. Thats alot of RPM for crusiing without an overdrive. If you have a fairly hot engine combination, it would problaby like the 4.33's better. Problaby in the neighborhood of 2 tenths of performance in the quarter. Hard to say..... Hope this helps...
Fastcat and BOnes is right. They are lousy for highway driving! Generally the higher the # the better it is for the strip, but worse for real world drivng. I think the idea is to have the gears matched so the car is at redline at the 1/4 mile. Detroit Lockers are noisy too. If you plan on driving it stay around 3.50+-. Less wear and tear on the engine too.
The new Detroit Lockers (those made beginning about ten years ago) have a few internal modifications from the original design so that they are no longer noisey. In fact they are silent.
The ones made in the 1960's are famous for the ratcheting noise made when going around a sharp corner such as when turning into a driveway at low speed. The noise is very similar to what you hear as a roller coaster creeps up its initial hil toward the release point. Clack Clack Clack Clack............Wheeeeeeeee!
Im still not 100% sure what you are wanting to know but maybe this will help. Other than the ratios which I have already explained you have the actual differentials which have also been touched upon here. The detrtroit locker and the traction lock. The detroit locker uses a series or ratchets than engage and disengage as you turn a corner. The traction lock uses cluthces and friction to slip when you go around a corner. For about 95% of the cars out there the traction lock is more than sufficient. In fact I had a 4.30 Traction lock pumpkin in my Mustang for awhile and ran in the low 11's in the quarter. Never any problems.. this answer your questions?