Leady:
Back when I was a boy, DC-9 times MEL-SYD would often be as least as quick as a B727 (certainly rarely any slower). Far better initial acceleration aided by a simpe flap retraction profile, and the ability to maintain high speed until much, much closer to the field tended to balance out the B727's higher cruising Mach.
And Down3gr, at least one of the DC-9 overtaking the Boeing incidents involved an AN DC-9 with the overspeed warning CB pulled.
Doubtless Emeritus, a DC-9 operator par excellence, can expand on this...