Agree with Jon Above^^^^^ it's more down to the area, phone etc signal strength rather than the software.. had Strava and Endomondo running both at same time on most rides and not had an issue. only really see a slight difference in Endomondo's distances it says compared to the Strava distanace, oh and the auto pause function on Endomondo constantly saying "Auto paused" "Auto resumed" as some of you have heard on rides... as it has trouble when you actually stop picking up gps positions, this can be turned off but then you only get a total time and not an actual moving time...
Strava has a better ability on this and has a total time and moving time.....
Also have a look at
http://veloviewer.com once registered on Strava, as it links into your account. This is a total of all your rides and timings in one place.. kinda cool if you like this sort of stuff
Now go out and get some of those Strava segments and KOM's