I think that many people know these two brands from the marketing and the fact that they are in two huge retail stores (best buy (rf) circuit city (mtx)).
i think that rf wins both, b/c usually u don't even hear of someone having an mtx amp unless is that 8100 or something like that. but then again when you talk about subs a lot of people respect the mtx's 8 series... i think it'd be an hard decision to choose overall which is better, but in the end possibly mtx just for the simple fact that they deal w/xtant too and their amps are the shyt.
but then again if u ask me in 2 hrs my decision would change, haha