Loaded questions.
The "best" is often debated, and at times debated HOTLY.
They can get to 130-140dB depending on the data you look at. (They STILL have a supersonic crack, so they'll sound like an unsuppressed .22LR)
You'll need to do some reading and decide for yourself. I prefer Ops Inc's suppressors personally, but Thunderbeast impresses me as does AAC, Silencerco, and Sure Fire.
No easy way to answer this question, that is for certain.