I had heard the Q-jets were difficult to work with/rebuild, so I tried the Holley spread bore. Bad decision. Afterward, I rebuilt the QJ and reinstalled it on my Corvette. I've told many people since then that I'm evidently
too stupid to know that I can't do something because it turned out fine.
I've rebuilt a number of them over the years and always (knock wood) had success.
Smaller primaries for economy; HUGE secondaries for performance.
Limited tuning capabilities
But overall, I'll take a QJ over a Holley
spread bore 10:1.