I’m a power match user and have also noticed the slow ERG response in Zwift compared to TR. Stages Gen2 left crank PM and Kickr V4 trainer.
I’ve done a few workouts in Zwift now and have noticed it seems to be harder to keep my cadence up and workouts generally feel a lot harder than they should.
Did some searching around and think I may be experiencing this, as yet unproven, phenomenon.
Easier going uphill in ERG mode,harder downhill - Bugs and Support - Zwift Forums
Interestingly I’ve always noticed this when doing the workout in TR and just free riding in Zwift, and have posted up about it on here, although how Zwift can be controlling the trainer resistance when controllable trainer is not actually selected is beyond me. But definitely more noticeable when doing the workout in Zwift.
TR & Zwift side by side power weirdness - TrainerRoad Software - TrainerRoad