what makes an emu faster than the other ?

[VIRGIN KLM]

It's even worse. Everything, I mean everything on NDS is binded to CPU's clocks. So if you overclock your CPU on NDS it won't only affect speed and FPS but sound too. Since the CPU will run on higher clocks the ADPCM samples it uses for it's SPU will be played back faster and in a higher sample rate than they supposed to (it will sound like it's on a higher pitch) so the visual and audio result you'll get from an overclocked NDS is exactly the same as a video being played back at fast forward.

Gamecube and Wii (Dolphin) though are not the same, they fall in the case of PS2 (PCSX). Overclocking it's CPU may (not importantly) benefit internal slowdowns at cost of accuracy of synced stuff.