Generally the higher the ratio the stronger the diff so a 4.3 ratio is stronger than a 5.1. I am told this is because the diff with the fewer amount of teeth on the same circumerance crown wheel therefore has broader teeth and so is stronger??
Also the 4 pinion diffs are stronger than the two pinion diffs. The diffs behind the six cylinder versions of the surf are stronger again with extra webbing on the sides to stiffen the third member over its length.
If you get one with an lsd get it tightened up because the standard ones suck!!!
http://home.4x4wire.com/erik/diffs/ - heaps of good info about yota diffs
