It's right around 3 dB per segment, maybe 4 depending on the load. I don't have the exact numbers, but hopefully can offer some comparison.
Personally, I see 12" as just absolute performance. 10 for when performance matters, but you need a bit shorter size. 8" would be more my hunting type load, where you want to take the edge off but you won't be shooting much. 6" does some, but it doesn't really make it nearly as quiet.
6" purely defense where you need a small overall package.
8" hunting, little loud but a few shots should be fine.
10" performance but a little size shaved off. (range, shooting clays, competition, etc)
12" is "impress everyone" size.
I would probably run 10" for just normal every day use, but 8" if I was out bird hunting. For low recoil 2 3/4" buck, either 8 or 10 and base it off if you want better suppression or if size is super important.