Back in time we used to use only Caldwell in our Pat Trap, no significant issues that I recall. When we started sporting clays about 12 years ago we had excessive breakage. Switched to White Flyer and the problem went away. Its not only the target that breaks in the machine that is wasted. Usually a broken target results in debris in the machine which needs to be cleared, so a broken target may result in loosing another 1, 2 or 3 other targets. If you are hosting sporting clays competitions, broken targets will not make you any friends among the shooters. Bottom line, I think we were better off with White Flyer even though they cost more, now $20 for a case which is up about 50% from what it was when we first started using them.
I think most of the sporting clays clubs in Western Canada are using White Flyer, probably a good reason why.