Voodoo has lots of good reviews. If you're just looking for something with more power, that's definitely going to do it, and it wraps around the frame to look nice. but any of the "kit" expansion pipes would increase power, just not as much as a custom made pipe, or a well made 70cc pipe. Please note all the expansion pipes you see on the vendor sites are designed for a 47cc engine, that means you'll get maximum effect with a 48cc engine. However that doesnt mean it'll make you faster than a 66cc (though odds are good if the 66 is stock). A 66cc with a proper 70cc pipe will haul ass a whole lot quicker than a 48cc with a 47cc pipe.
The poo poo pipe is just there for show as far as I can tell, a long, straight pipe with no expansion chamber. It should give it a lower tone, however, I'd have to test the one I have to see, but I've heard people say "it sounds more like a motorcycle now", but dont expect any performance boost.