It's not a matter of accuracy FYI, it's a matter of how your governing rules require you to log your time. For example, US Air Force (FORM 781) dicate the time convention and there are several out there. HH:MM is not necessarily better, in fact, you may find yourself with less time in the end if comparing against someone logging with the Logbook Pro's use of the Air Force 781 format. It all really depends, long story longer, we are intending to provide the utmost in flexibility with the next major version to allow you, the user and pilot, to choose your conversion or logging system.
Thank you for your continued patience.