I'm def a fan of the concave type pads, for me they're more manuverable...easier to work in tight areas using just the edge/side of the pad and such.
I have used the CCS "flat bottom" type pads and thought they worked fine. I didn't really notice the skipping others have. I more didn't like having to use the entire 6.5" pad surface on the paint.
My concave pads round from the bottom to the side...while the
CCS pads seem to be more of a 90 degree angle. I prefer the rounding sides of the concave type pads.
The problem is, I'm having trouble finding the older style concave pads...most pads seem to now have flat bottoms.