I don't think it will make enough difference to matter. .357 is enough to damage hearing, permanently. I don't know if it is worse inside a room, but I can tell you from personal experience that it SEEMS worse.
And, if the only time you shoot without hearing protection is in gravest extreme, you will recover most of your hearing, eventually.
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All else being equal (and it almost never is) bigger bullets tend to work better.
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