Hello Morpheus! I too, used to be a rezound owner who switched to the HTC One.
And by God does the HTC one fly. You absolutely cannot compare the One to the rezound in ANY manner. I can play Asphalt 8 on the highest setting with zero lag, while on the rezound I will lag at least a few times per game on the lowest setting.
Camera in lowlight is stellar. Once again no comparison. I have actually managed to capture pictures of clouds at midnight, although the iso is noisy at night, it's still visible. (since your a photographer, shutter speed drops to 1/7, iso 2000, aperture 2.0)
Battery: comparing my stock rezound battery to the stock One battery, it's better on the one. I get a little over 3 hours of screen on time on the one Co pared to just barely or under 2 hours on the rezound. I rarely toggle 4g though now. The battery life feels as if it lasts 3 times longer though.
Sent from my ADR6425LVW using xda app-developers app