Any argument about whether steel or aluminum is more prone to brittle failure (snapping vs, bending) is pointless.

Both materials encompass numerous alloys and conditions (temper). Many steel alloys can be heat-treated to properties ranging to almost silly putty-soft to glass hard, likewise with aluminum, though it's range is usually narrower.

The mode of failure is also influenced by design and assembly factors, such as cuts, notches, plating, welding, etc, and by the degree and number of flex cycles to which they're subjected.

Without dealing in the specifics, debating predicted modes of failure is like arguing about which river is deeper, the Hudson or Mississippi.