Great update.
Just bought the P7 myself after testing many of the same headsets (+ Beyerdynamic T770 pro 32ohm and AKG K545).
Tend to agree with your rankings. Would have bought the HP50 if it hadn't been for the ear cups being slightly too small - or should I say too shallow as my right ear was touching the driver (my left was just OK). Great sound especially considering the price. In my opinion the design looks rather stupid though, but I could live with that as I don't by headsets to look "cool" anyway.
Really liked the Momentum as well, but as for many others the fit on those are just so random. Partly on ear and partly over ear. Worst fitting "premium" headset I have ever tried, but I guess that is fairly individual. As mentioned not key to me, but they are by far the best looking and most portable to me (having around your neck). I actually love how they look.
Never tried the H6 so ended up with the P7. Not a bass junky, but it sounded like H6 would have a bit too little for me. For example I found the T770 boring. And I'm not a big fan of round ear cups. Seems so pointless to me as few ears are round.
P7 are not worth the money compared to HP50 in my opinion, but they are just so much more comfortable with my head and ears. Not only the ear cups, but also the headband (not as good as Momentum though). With the "flat" HP50 ear band it rests on such a small area just on top of my head. As they are not exactly heavy I guess it could have been just within acceptable, but with the P7 I had none of these issues. Still don't understand why the P7 got such a thick and hard headband. Would have looked so much better if it had been slimmer and as it is so firm the thickness doesn't add any value in terms of comfort. Also would have liked memory foam. I can only guess they have used a different material because of the "space" it creates - which might have an effect on the sound. I don't know. In terms of comfort it certainly doesn't make any sense.