I started wet tumbling this past weekend... amazing results. 200 pieces of 308 per batch with a Frankford dryer... easy... except I had 5 pins “escape” in the sink, with a garbage disposal. Need to pay more attention! Regarding mouth peening… I trim every load cycle no concerns.
Ah, the lost pin...
I use a cement mixer and 60 or 80lbs of pins. I forget. It's the only way to go for bulk, large cases or volumes (if you load for an M2HB then this won't even be a question of which is better) but I'm not so sure the pins really do much... I have a vibratory tumbler and a cheap-o Hornady US cleaner (it came with a bunch of XTP's, couldn't refuse). Each one has it's pros and cons.
US cleaner is best for accuracy and how I can say that is because the brass doesn't bang against anything. It just sits there, goes in dirty and comes out clean. But I think I burned up that Hornady cleaner (it rattles and shit now) trying to do BMG cases back before I got the cement mixer. If you don't load volume or 100+ large cases, this is by far the way to go.
Vibratory tumbler is a good stand by and everyone should have one. I use it for finishing off brass or loaded ammo (I know, but I use a lot of media and don't really give a shit...). It's good for removing lube from cases prior to loading.
Wet tumbler works well for large volume but that's it. That goddamn lost pin fucks it all up and you will lose sleep over it. I've heard it's not that big of a deal in most cases, that most times a stray pin will just blow out the barrel with no consequences (unless you have a can on it, which likely I will). And it's best to only use it for bulk cleaning prior to decapping. Dry tumbling will remove lube better and give one last chance to shake out any pins (hopefully, at least won't be adding any). So you need the vibratory tumbler anyway IMO/E.
I'd also get the Dillon rotary basket or whatever the hell it's called. It rotates and shakes out any water or pins or dry media. It's a damn useful tool for sure (wish I had one made out of a beer keg but hey, can't have it all).
So unless you do great volume or large cases, get the vibratory tumbler and the rotary basket and call it a day. If you have the money or need (or just find it for a killer deal like I did) then get the US cleaner too. Small wet tumblers? I don't understand 'em, if you don't need a cement mixer then you probably don't need to wet tumble either.
Oh, you can also just wipe 'em off one at a time and I've done that too...