I have a mixture of all three, and several sizes on hand between 1/4", 3/8"lp, .325", 3/8" and .404". My 28" and shorter loops are all full comp. For my 36" 3/8 bar for my 660, I have full-comp, semi-skip, and skip. I lie semi the best, as it's the best compromise between smooth cutting, low grabbiness w/smaller stuff, and good chip clearance. The full-skip is reserved for softwoods, where the chips tend to be large, and other chains stall in the cut. For really nasty jobs, I have a 32" .404 bar for the 660, and it's for stumping big uglies.