Without getting scientific, here's how I understand this topic:
Light is the most essential ingredient of all images.There should be no question that a larger sensor contains more pixels than a smaller sensor. With more pixels, the sensor is physically capable of collecting more units of light (photons). With more light, you get a better image.

So why do we see such superb image quality with the smaller crop, MFT or iPhone sensors?

Why are there some smaller sensor cameras that have now earned "professional" status (e.g. Nikon D500) due to their superb performance in low light conditions?

One answer, IMO, is the technological advances of the specific camera and in particular how efficiently the pixels absorb and process the amount and quality of light that enters through the lens. Thus, sensor technology has been able to prove once again, the truism that "less is more". Sometimes...

Add to the improvements in sensor technology yet other advances and improvements such as in body and in lens image stabilization, lens quality, auto focus, etc., and we have lots of material for lively and stimulating discussion within our UHH family. But none of the advances can replace the fundamental elements of the exposure triangle, all of which address and affect one subject: light the quintessential ingredient of photography.
So, the more things change, the more they stay the same.

BJW

Hi Dave,
I reviewed both camera specs again. I was wrong about the Sony being a constant f2.8 through the zoom range. Like the Nikon it goes up to f6.3 when you go into telephoto zoom. Both cameras have macro capability and allow focusing at 1cm in wifde angle mode. I was also wrong about the Sony shooting 4K video. Both cameras shoot HD video at 1920x1080 resolution. The Nikon is about $80 cheaper. I think they both are pretty equal in capability. The Nikon has a lower wide angle focusing range (23mm) which is better for landscapes. The difference in telephoto won't matter much. The 900mm telephoto range on the Nikon is as much as is usable for good bird pics. The low light capability is not generally as advertised. Once you get past iso 800 on most cameras, you run into unacceptable noise. So the cameras are probably equal in usable low light capabilities. The only thing I don't see on the nikon is timed exposures longer than 1 second. I'm not sure if either camera has a manual mode. You will need to buy a couple of sets of rechargeable batteries and a charger with either camera, as they will eat up regular batteries quickly. Another thing you will want is an sd card reader (fairly cheap) so you can insert the card into the reader and transfer your pics on the computer without going through the camera. It doesn't matter what camera or computer you have, done that way. You can tilt the lcd screen or not, up to you.
Bob