Looking at both sets of pipes the JHA's have a much larger chamber which I found on my '21 didn't fit the fairing.
The Dog Fights, I think are just as good. The welding is as neat and the chamber is slimmer. They also have a nice little bracket under them which bolts the two chambers together where the JHA's don't. I also think the Dog fights fit much better.
The main criticism with the Dog fights seems to be there power. They are quite critical on set up.
Personally, now having run both sets of early and late JHA's and Dog fights, I would go for the Dog fights.
These graphs show the Dog fights on a stock '21 motor with open carbs and HRC jet kit, back to back with the '21 F3 motor also running Dog fights.
These are the Dog fights fitted with HRC cans. The JHA finish quite abit higher.
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If I have to take the carbs off once more...