There will always be a difference between gps recorded and distance speed recorded by the rotation of the wheel, which if set up right will be more accurate, thats why I got the speed/cadence sensor, also different sites software read and interpret the data slightly differently, ride with gps is bad for time ridden and actual time this then effects the avg speed.
I thought I had done better than I did on the run to the hospital, must have been the level crossing closed, but I did get one nice p.b.
http://app.strava.com/activities/42663940#717584005 6's quicker from 14.2 to 15mph.
The ride home I did a 21 mile loop ride I got 3 p.b's I actually did this ride to see if I could improve on this
http://app.strava.com/activities/42663947#717584079 no such luck it was the last mile and 1/2 or so with a northerly head wind, 39's slower than my best set in Sep, must have been a hell of a tailwind back then.
This one I am quite pleased with
http://app.strava.com/activities/42663947#717584073 7's quicker an increase from 11.6 to 12.4mph ( I think that where the segment ends has a lot to with it, traffic)