We have little coyotes here, little fox, lots of coon, and some areas lots of dogs afield, too. I run mostly #2s (longs and coils both) and lose precious few coyotes from my #2 longs. Jaw spread is about same as 1.5 coil, but much better mechanical holding power over that similar-sized coil. However, once the snow flies, I go to 1.75 or #2 coiled 4x4s. They seem to bust crust and snow much better for me. I can add beefer springs to my #2 longs, but by design of that trap, once the trap jaws are fully opened up, you don't need to exert much force to keep the trap "open" and you only have to do that really to the one jaw. If it doesn't take me that much effort to keep it open, then a slight freeze can do it too. But, a stoutly springed coil gets harder to hold open the more you open up those springs.
Its simple mechanics, by design a coil has the least spring resistance once the trap is fully closed, more and more resistance as the jaws are forced open and the spring levers pushed down. But, a long spring has more holding power on the top end at closure mostly because of how high they tend to lock up on the jaws when the trap is closed. open up the jaws, and the springs can be held at full compression easily with just the one power driven jaw much more easily than a coil at this same point.
When I do use longs in late season, I really make sure that no moist soil touches the jaws or top of the springs so that if things freeze up my trap won't also.
