I compared both.
Assioma Duo registered into Garmin Edge 520 and Kickr Core into The Sufferfest app.
Both spindown and zeroing performed properly before the test.
I saw less than 1% difference for average and normalized power and below you have the overall comparison.
I was pretty happy that I was measuring power based on Assiomas only for outdoor rides.
However, my Kickr unit got electronic problems, and the trainer I bought as a replacement is not showing comparable results. I hope the company will find a way to fix/improve it.
Cheers!