Frankford Arsenal "platinum" stainless tumbler is the ONLY way to go.
There will be some old farts that will say that they are happy with their vibratory tumblers, but you probably won't find a single person on the whole internet that will recommend it after using the FA tumbler.
You'll pay more upfront for the FA, but your brass will come out WAY cleaner, and WAY faster. Time saved in the long run is worth a lot more than a couple of hundred bucks more you would pay for the FA.
I've used both the vibratory and ultrasonic ones before, and now looking back I cant figure out why I didn't switch to FA sooner.