I know that I compare actual riding times. How are you comparing the two? How are you measuring your ride times? With the 510 and 810 I use I am able to break down actual moving time vs elapsed time. This seems to be the best way to compare the two for me, not to mention you can pull up both trips and break down durations on particular segments (To/ from). I am fairly even on a commute that has similar ending elevations when I take the elapsed time out of the equation. Lights run on different schedules so you have to figure that can cause longer overall time for one or the other.