Regarding that new DVD about the early Beatles and Pete Best, what was really interesting is that the people who actually saw the original 5-piece line-up (with Stu on bass) all agree that they sounded amazing!
Apparently, towards the end of Stu's membership of the band, he wasn't a bad bassist - not good, but not bad either. He played only the root note (I think that's the term) 4 beats in the bar on the bass, following the chords AND in tune. Pete Best complimented Stu's playing on the bass drum by also keeping to the 4 beats in the bar.
The people who saw them back then all say they had such a pounding beat but when Paul took over on bass, that beat disappeared because Paul could obviously play the proper bass parts. Stu's departure may also have served to highlight any failings in Pete's playing.