Emulation dissucion

[Lupac]

Today I downloaded the latest release of ppsspp and loaded and Iso for the first time. I played 3rd Birthday and am very impressed on how well it runs this game. I have been following ppsspp development and in a short amount of time its made huge progress.
It's left me wondering why there isn't this kind of progress on a Nintendo DS emulator. Are Nintendo DS emulators slow because the lack of a team/organized effort or is it because NDS is harder to emulate?