Hmph. So I got the Mini. I actually really like it. The size really is perfect, and it really does feel a lot smaller than the original One. Also, that Sony announcement didn't come to fruition....however, the battery life is just AWFUL. It's really bad. Performance is ok, noticeably slower than the One (I think it's the RAM more so than processor), but I could live with that....but man, the battery. I don't know if I can do it. Might have to swap for a Moto X.
Do you have Greenify and/or Snapdragon BatteryGuru? I would run those and give it a week or two of condititoning before decifing to change phones. It's dissappointing to hear that the battery is bad out of the box, though.