With RideWithGPS, for real-time tracking, you can hold any data field down, and change what is displayed. Sliding right or left, and you have 2 pages of current data to display.
Options include actual elevation, and real-time elevation gain. And, I find that the gain is off by a factor of about 2x.
Both RideWithGPS and Strava do post ride processing, so the post-ride data is closer.
If I count valleys to peaks, my climbing is usually more than I would expect, especially with a lot of flat riding. But, while riding, one might not realize that one is doing a slow climb/descent, or the effects of very mild rollers or dips in the road.
Nonetheless, GPS data is generally quite accurate for X/Y locations depending on the recording device, but relatively inaccurate for vertical data.
With RideWithGPS, I've been actually climbing (1% or 2%), and watched the elevation drop by a couple of meters.
Anyway, the climbing data is representative, but I do take it a bit with a grain of salt.
Some devices have built in barometers which significantly improve vertical data tracking, although I wonder if the barometers are also responsible for some of the strange anomalies that are found in a large number of Strava segments.