This is a problem of comparing apples to oranges, while forgetting that there are a number of varieties of both oranges and apples.

Gauges and diameters vary in every material, and in the case of aluminum they vary greatly. Talking about "dentability" based on coarse generalities is meaningless. In fact, even the same material in the same gauge will have varying "dentability" based on shape.

You can see this if you look at auto bodies. Any single body panel is of uniform thickness and material, but resistance to denting varies. Go to any car (preferably your own), and press on a fender or door panel where it's relatively flat and it'll yield easily. Now look for an area of greater curvature, and press with equal force and you'll note greater resistance.

If you don't have a car to play with you can do the same experiment with a hard boiled egg (or raw if you prefer) tap the blunt (flat) end and it cracks easily, but it'll take noticeably harder tapping to break the pointy end.

This is to show that dentability is a complex consideration, which depends on multiple factors, and generalization is useless.

BTW - in all fairness to those with previous mythconceptions on this subject, I should note that at identical thickness and curvature an aluminum frame will dent easier than a steel one.

The only conclusion we can accurately draw on this subject is that there are no conclusions because of the range of variables.