When comparing the 20 Classic series, Set #1 is more incut and easier on steep walls, whereas Set #2 is less incut and easiest on lower angled walls.
Set #1 has a variety of rounded nubs and flat edges that you can toe into. Many shapes are omnidirectional, which means you can rotate them for a less positive version.
This size of foothold is only appropriate to be used with commercial climbing shoes.