The PD carbs work well, and provide finely tuned mixture when using the stock 4 to4 exhaust (higher internal pressure) and the stock air induction. These carbs can be tuned more precisely than the old style carbs. They had to, in order to meet 1978 US EPA low hydrocarbon idle requirements.
Changing exhaust an intake components with these carbs almost always forces them to provide lean mixtures, due to the smaller fuel metering orifices.
Correct the metering orifices, and they actually a superior carb type than prior models.
The older style is a "sloppier" carb and they came jetted for more open exhaust types. So, they need less adjustment to run acceptably, particularly with non-stock intake and exhaust modifications.
In stock form, the PD equipped bike had good street power and got 50MPG or better.
The early carbs can also make good power, but most struggle to get better than 45MPG.
This metric alone would indicates the PDs are actually better carbs when tuned properly. Tuning properly is something many homebrewers struggle with, so they opt for the older carbs and dismiss engine operational efficiency.
I say use what you have and tune for the mods you make. But, if you have open exhaust, you are better off with 022A internal parts on the earlier carbs.
My CB550Fs with stock muffler also get 50MPG with the 069A carbs, and they aren't slow, either. There aren't any US 78 CB550F models, because they couldn't quite make the idle hydrocarbon idle EPA test with the old style carbs. Finer tuning not available, as on the PD carbs, so model was discontinued rather than retrofit the PD carbs to it. I'm sure low sales figures also factored into the decision for return-on-engineering-change costs.
Cheers,
