The climbing is not accurate on any of the sites that I am aware of. It is a function of the data being fed to the site from wherever all these programmers get it. You really have to ride the route with an altimeter or GPS to get an accurae number.
Two different users can enter the same routes and have different total climbing just depending on the number of waypoints they enter.
I've had very good luck with routeslip since they guy is upgrading it steadily. Unfortunately, the site has become so popular it's outgrown the server. They need sponsors. Maybe TE?
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.