Quoted from dmbjunky:
So do people have both a tumbler and a ultrasonic cleaner? I was thinking of getting a tumbler because I thought it could clean both metal and plastic.
An ultrasonic is a CLEANER. It blows out crap from the crevasses and such.
A tumbler is a POLISHER. It brings surfaces up to a high polish (it can remove corrosion too, if you use the right media).