just what it says ones long cage the others short, short cages are used when you have a fear of hitting the mech on something (rocks etc), but with this you can experience some problems with not being able to properly use some gears (granny gears to be precise). I have both types and to be honest you don't really know the difference as the granny gears don't get used much anyway and i don't hit many rocks either (ok sometimes but they hit me honest).
