So in no way are these similar to each other even though they are identical in size and shape and have pretty much identical drivers? Besides the pads and another being semi open, there are only minimal differences. Pro80 has two open holes at the back of the driver, hi2050 has only one. Pro80 has more space in the center of the cups, hi2050 has broader damping material so there is space only over the center hole. These are propably the most identical sounding open vs closed headphones ever.
I agree that pro80 is better. It sounds exactly as good as 2050 but also has more bass and provides isolation. Usually more bass affects the mids in negative way and isolation compromises soundstage. Not in this case so Pro is superior. However if a person doesnt need isolation and doesn't care for bass at all there is NO reason to pay extra for pro80.
Also pro80 needs more voltage to be driven at same level of sound. Difference is not huge, but it is there. If listening level is not adjusted between comparing the headphones the louder one (pro80) will sound better.