This is a timely topic as I do some product testing for Kinetic and I've been comparing the ERG behavior between programs, primarily Zwift and Trainerroad. My experience there is that the reported power tends to "wag" around a bit more with Zwift and presents some challenges with steep increases in power. Comparatively on TR the transitions felt more natural (easier to keep on top of the gearing to avoid a low cadence death spin) and the power figure was much more steady and true to the target.

I'm doing some testing in the weeks ahead with Bluetooth over FTMS (not yet supported by Zwift) and it will be interesting to see how it all comes together.