SNES Emulator speed on NDS?

I have both a NDS and a PSP but the problem with my PSP (Phat, CFW) is that some games on the SNES emulator like Super Mario RPG run SUPER slow. I'm looking into getting a Datel Games n music for my DS so i can play my SNES games on my DS. So my question: is the SNES emulator any better on a NDS or are they just as slow as a PSP? and if they arn't would it be better to get something else other than a Datel games n music? maybe something else for better speed?