Well, tell me if my logics are incorrect here.
Something written in ASM is logically faster than something written in C/c++/whatever, unless the ASM one is horribly unoptimized (which in the case of ZNES, i highly doubt its unoptimized).
A unoptimized filter, for either emulator, is going to take the same hit, wont it?
Then wouldnt a emulator written in ASM preform better, due to the fact that its more efficient?
I would believe ZSNES would take slightly less cpu compared to Snes9x, simply because a matter of coding differences.
eh? =p