Originally Posted by willtsmith_nwi
They all operate pretty much the same way. The guts are different and some will work in mud (Time, Egg Beaters, AtomLab) while others will not (Shimano and pretty much everybody else).
Don't forget Speedplay Frogs. Completely different from the rest. They work in all but the stickiest of mud and there's no spring force to hold your feet in any particular place. They feel a bit funny at first, but once you get used to them - just a couple of rides - they're awesome!