Sony Alpha a900

“There is 1-1.5 stops of difference. That is, not only in "crop factor" but in everything -- in noise performance, DOF, DR, the lot. This is not the complete truth though, as generational differences will be more important -- my a6600 absolutely smokes my a900 in noise performance, for example. But generally for the same amount of pixels in FF/APS sensors of the same generation, the difference will be 1-1.5 stops. Now it can be argued that this isn't much, that this is uninteresting provided light is good, and that slightly better DOF is a pro. But there is a difference, and minute differences can certainly trigger purchase impulses. ;-) Also, 35mm in film didn't win the format wars because it was "the best", but because it was a reasonable compromise; good quality in a very portable (even pocketable) package. A smaller sensor can mean a smaller camera, but "too small" is a thing (I have 3D printed an extension to the grip of my a6600), and diffraction will get you if the sensor gets too small as the 4/3 systems have belatedly discovered. Lastly, innovations have arrived at the FF cameras first, just watch how long it took IBIS to arrive in the Sony APS-C models! It was the a6500, even though the full-frame a7ii had it two years before, the APS line was leading the FF line by several years, and almost all Sony APS SLRs had it.”