Agree with canklecat plus: in addition to biking, I also hike once a week with a friend and until recently we would both use MapMyHike app on our Android phones. The same app on the same OS, but different phone hardware, would record different distances for the two of us, often as much as .25 - .5 mile difference on a 6 mile hike - even when we purposely started and stopped the app at the exact same times.

Under Armour pulled MapMyHike from Android, I've been trying to use Strava for hiking but found it very buggy for that, will probably try MapMyWalk which UnderArmour seems to still support on Android.