>>4307708>That's only because of the larger photosites, a benefit taken away by projecting less light onto them.FF has less noise due to higher SNR overall (larger surface area collecting more light). With gapless micro lenses pixel size is almost irrelevant. I say "almost" because it starts to become relevant at extreme ISOs (i.e. 50k and higher). Below that it's just not a significant factor. People like to point to the A7R V as a counter example, but the A7R IV has the same pixel density and doesn't break the pattern. Something else is going on in the V's electronics.
Now if the AF sensors are the same size and tech then yes, apsc will have a ~1ev AF advantage when a teleconverter is on FF. Same size/tech is not necessarily a safe assumption though as manufacturers like to throw their best into FF. And for mirrorless a FF AF sensor can be larger than an apsc one without noticeable disruption to the image. Beyond that, teleconverters tend to be used in brighter light. If you're above a certain threshold it's not going to matter.
