Jonathan Huyer
www.huyerperspectives.com
Here is the thread I referenced.
Unfortunately, the link is broken to AlanF's analysis, but I recall he was taking DXOMark's P-Mpix (perceived megapixels) and comparing APS-C to FF. As the thread and Alan's analysis are a few years old, it is always possible that there have been improvements (better microlenses?). While I can not think of an APS-C camera with the same MP of a FF out of the current lineup, the 5DIV vs the 90D, if anything, should favor the 32.5 MP sensor and 3 year more modern 90D. Yet, I can still see a slight FF advantage here. So, same framing, distance adjusted, the 90D has more pixels on target, yet I'd take the 5DIV image quality over the 90D. It is getting close, though.