I personally do a better job sucking on an uncut dick, but that's probably because I find them more arousing.
A "proper blowjob" for me is one when I lay down spread my legs wide, have my whole piece of meat eaten, my nuts licked my asshole stimulated until I am drained.
I know that I give a "proper blowjob" when the guy screams and moans with pleasure and unloads with force