Jim, formica solid surface is polyester resin with ATH mineral filler. ATH is white in color, so when you scratch SS it shows a white line. The lighter the color the less scratches show. SS can be sanded to remove the scratches. As far as your top cracking at the corner, that indicates to me poor fabrication. All inside corners should have a radius and solid corner blocks under. If this is not the case I would contact the fabricator and have him look at it. If it is still under warranty I would call Formica and explain the situation.
Hi Max, Corian and many others use Acrylic resin with the ATH filler, Acrylic is not as "brittle" as polyester material, tho, the amount of resin vs ATH makes a huge difference. Avonite makes a "glass product" which is almost 100%% resin, and is much more brittle and subject to cracking with movement.
The lighter color SS materials are a good option for RV's. With adequate support underneath they will give you great service, and, they are easily renewed. I would get a matt or low gloss finish rather than a high gloss, as they are easier to care for. A scotch brite pad is the final sanding on both those finishes.
Good luck !