If you put the same recipes into different barrels and have them ferment for the same duration, you will get the same result. Thus the metavalue of the drinks will be equal.
it seemed sort of random to me... I had set up all the barrels at the same time, and then tapped them all as fast as i could. I ended up getting odd values tacked at the end of the rum with :89800 to :89999 even from the same barrel. I instead abandoned the trade-o-mat and used a RP2 contraption to sell the booze. This is on a tekkit server, i am not sure if you pay any attention to that, if not i should post on tekkit forums?