The Street Demon has what's called "triple stacked" boosters. They "somehow" atomize the fuel better......and I can attest to that, because I very recently swapped on an Edelbrock 750 in place of my 625 Street Demon. The 750 had a little rougher idle......the camshaft came through a little more. That's proof right there the Street Demon is a better mixer......at least at idle. I didn't have a chance to leave the Edelbrock on as one of the floats was compromised and it eventually started flooding, so I swapped the Street Demon back on. On this Ford 400, it "runs out" of primaries pretty quick, so that tells me it needs more carburetor.......well....at least bigger primaries. While it had the 750 on it, it did have WAY better throttle response, so I will likely try the 750 again and see if I can get it to tune out. I think it will be more efficient in the long run, because the Street Demon gets into the secondaries pretty "quick" if that makes sense. Of course, ultimately, I'd love to try a 750 Street Demon, but funds just won't allow.