I think a lot of it is personal preference and tuning abilities.
Some of it has to do with your prior experience. If you tried everything you could think of, and it still leaked, blah you're not likely to recommend one.
I've had nothing but good results with QJ since my 1st adventure in 1970, so I'm comfortable with them.
OTOH, Carter ThermoQuads make me nervous, even though my 1974 Dart 360 runs just fine.
Some older stuff can be sorted out, if you just do some homework. Here's an older example for Harleys:
http://www.victorylibrary.com/L-BK.htm
