I think there is a fair bit of variability with the between trainers. I have a First Gen Kickr and use it as my “backup” trainer with the Neo as my primary.
I worked with Wahoo support a couple years ago because I had determine that there was a discrepancy between the power readings on the Kickr vs my power meters on my bikes. The first gen Kickr used a different method to calculate power via a strain gauge. Wahoo removed the strain gauge in subsequent Kickr and used the brake to calculate power which was thought to be more accurate. They came out with an update for the first gen Kickr that essentially disabled the strain gauge and turned it into a second gen device by using the brake to calculate the power. Wahoo support recommended I try this since I was having issues.
I did this but the accuracy did not improve and perhaps even got a little worse. However power match worked great with TR, so at least with TR workouts it was not an issue as long as I used a bike with a PM on it. I was doing some Sufferfest workouts at the time though and these were a pain since power match didn’t work with Sufferfest.
Wahoo support said there really wasn’t anything else that could be done regarding the high power readings and that some of the Kickr’s do read differently than the PM’s on bikes.
Lately I’ve been using my Kickr again while waiting for a new free hub for my Neo. For fun I sync’d up my Garmin with the Kickr during last night’s workout. It was SSB between 235 - 250 watts (again I was using power match so that was what my Quarq was reading). However my Garmin was reading 265 - 280 (getting data from Kickr).
The only other weird thing the first gen Kickr does is every workout or two it suddenly raises the resistance super high for a half second or so. It shows up as a big spike in my workout. Googling this issue shows this happened with some first gen Kickrs but I don’t think is a problem with newer ones. The Neo does not do this. Its a pain when it happens but happens infrequently enough that it isn’t a huge deal. On the plus side I had none of the mechanical issues that the 2018 Kickr’s are plagued with.