are you using it for security surveillance? if so it dont matter 2 licks what resolution your display is, more pixels is more data and better image.. you can zoom in on the recordings without loosing quality.. unless your streaming it to a 720p display only and never recording anything I can think of absolutely no reason to run a camera at 720p that is capable of better than that.
if your just saving it to disk, more resolution wont take any more cpu power.. you can run twice the resolution and half the frame rate and have the same storage requirements, and end up with better video.
have you looked at the price of HDD's lately? I record 24/7/365 on 7 cameras all 1080p or better and get near a month of archive storage.. lowering resolution to save on diskspace is like cutting your toes off to make your feet lighter thinking it'll help you run faster.
