My favorite, of those I've tried are Cat Whiskers. But from time to time someone writes they degrade performance more than other types. On some bows I've simply kept, for now, what the Bowyer or previous owner has on the string. So I have one with wool balls, Bojack, String Leaches, and Cat Whiskers. I did take the Spiders off my PAX when I arrived --I just have a hard time accepting four of those things aren't too much "slow down" on my string.
I traded for a very nice Checkmate several weeks ago (since traded it again). It came with these yarn-like strips, I think they are called "Tarantulas"? That bow was whisper quiet! When I have to make my self listen for the bow's sound instead of noticing it right off, I know I have a pretty quiet set-up.
I like that video test idea mentioned above!