My FAVE silencers are Beaver Balls or other types of fur silencers-but they are not terribly practical on a compound. But they are by far the coolest!

I think the factory BT silencers work very well , but when they have worn out/legs have torn off, I usually replace with a Sims Leech- They work a little better and it's a PITA to take the string off and re-thread the BT silencers over the string. I like the look and durability of the catwhiskers like Russ mentions the best, but once Sims came out with the leeches I never used catwhiskers again- the leeches work better IME.