In terms of SPL, two 10'' have more combined surface area as opposed to one 12''.
I may depend on your application, IMO, get the x.x.x, give over 1200 watts of nice clean power, put it in a ported box built to spec and hope for the best.
In terms of SQ its a no contest the brahma or x.x.x hav superior SQ.
But i think you'll be just as loud with a good x.x.x install.