For what it's worth, yes, I do find HPA much more consistent than Co2. Up here the temp varies from +30*C to -30*C (like you have to worry about that where you are!), but the velocity stays the same regardless.
As for numbers/grouping, you can get more power (consistently), and seeing as the velocity is steady, the groupings do benefit as a result (as long as I'm doing my part!)
It is alot more expensive to get set up for HPA, but worth it IMO.
????....Did I not answer fast enough?