Did a nice 35-ish mile ride today - about 1/2 rail-trail and 1/2 streets - started in Will County and ended in Cook County in Illinois.

Since I had a small issue with my speedometer, and my GPS generally shorts me about 1/2%, I checked my route with 4 online route mapping sites that would also give me something I did not have - elevation gained.
VeloRoutes.org gave me 34.65 miles and 780 ft of gain.
Bikely.com gave me 34.65 miles and 305 ft of gain.
BikeRouteToaster gave me 35.04 miles and 423ft of gain.
Gmap-Pedometer.com gave me 34.64 miles and no elevation gain, just a profile.

Any comments on who's elevation data comes from the most accurate source?