>>2842210I'm coming into this midway and might be misunderstanding what you're trying to argue, but if you want to use the rain analogy, what matters is that both containers will fill up to the same depth, and it's the same with sensors.
On a physics level, yes, you may have collected more light overall with the larger sensor, but you need less light to make the same exposure if that makes sense.
From a photographer's standpoint, it's irrelevant, because exposure at the same f/stop, shutter speed, and ISO will be the same regardless of whether the sensor is a 645 Phase One monster or a fingernail-sized P&S sensor.
The place where crop DOES matter is effective depth of field between lenses of the same focal length. As a general rule, a 1.5x sensor will result in a stop more depth of field compared to an FF sensor with a lens of equivalent focal length. (i.e. a 35 f/1.4 on 1.5x will similar to a 50 f/2 on FF, and you'd need a 25 f/1 on m43 to do the same.)
