sounds like the corded 3/8 0-2500 dewalt/makita/hitachi/b&d types are best...but like Corey said and i have tried and can verify is a dewalt 18v with about 1800 rpm works just as well if you have one.
what i've tried and can say does not work as well is an older dewalt 12v at around 1400 rpm.
i've found the higher speed really cuts down on the fuzz at the entry of the pocket hole.