Would there be a difference in video at night between 4K and 5k 30fps? In other words would both formats allow the same amount of light into the sensor?
Some of the Air 2S videos showing up on YT, have some night video clips and it looks pretty good. Though it was not mentioned specifically that I recall whether it was 4K or 5K.. The larger sensor will probably allow for better night video with less noise..
Light hitting the sensor will be the same. 5K could have more/less noise vs 4K depending on how it's read from the sensor, but my guess is it is very close. What makes a much larger difference is sensor size. The larger sensor vs the Air 2 will give a much better image in low light, due to larger pixels.