Collars - yeeesh. I've seen dogs killed by collars that fit too well (hunting dog who was hung to death on a picket gate) or too loose (sheltie who was hit and killed after slipping out of its collar being dragged to the groomer) - and I've known the terror of a loose/scared/running dog with NO collar....
I looked into breakaway collars, but they can separate when you are grabbing the dog to hold it back from whatever. Granted, Ben is only 20 lbs and ridiculously obedient (has a heel and recall the obedience folks would kill for...LOL!) - but there's always that ONE time you don't anticipate, and you need to be able to control your dog.... so I guess I'll stay with a conventional collar, and try to tone down the roughhousing (which actually isn't all that rough since both dogs are basically wimps)