Think of any imaging like pointillism, with grain (or pixels) being your paintbrush and the format is the canvas. If you have a stock like 500T, that's your paintbrush to make dots. Let's say that one paintbrush makes dots 1/2" across, and you have a canvas 25"x25", then you can only fit approx 2500 dots no matter what you paint. If you increase the size of the canvas, then you can increase the number of dots to make a more detailed, higher resolution image. This is akin to what happens when you move from super8 to 35mm on a given filmstock.
If you have a slower film, then that's like a smaller paintbrush: then you can fit more dots on a given canvas. This is why 50D shot on super8 can be so sharp and detailed. If you choose a larger format (like 35mm) then you have a much larger canvas compared to the grain size and you get much higher resolution and why 50D on that format is just spectacular.
More things happen with smaller formats. Normal lenses for super8 is 13mm, versus approx 32mm for super35, so usable lenses have a greater depth of field at normal apertures. Shallow dof is more an issue on super8... and yes: dirt, hair & grime and film weave in the gate is amplified on super8.
Edited by Jesse Andrewartha, 07 September 2016 - 06:33 PM.