I use the one that Talon Tunes sells. I don't know if it is the quietest, but it works fine for me. When I am in the back yard shooting, my wife who has ears like a hawk has eyes, does not hear me shooting.
The other reason is that it just fits in place of the shrouds end cap and does not need a threaded adapter.
It also looks like it belongs there rather than looking like a Coke can that has been painted black.