Surely in the instance of a laptop case, any potential "bouncing back" is more than negated by the crushing damage of a drop if your laptop is in a sleeve?
I'm simply saying that less damage will occur if it's in a rubberized sleeve vs. a hard shell.
The question was 'I heard a hard shell scratches the metal.' My response was yes, it does. In terms of protection, dropping a 2 thousand dollars laptop on the floor is never a good idea. But pretending that a flimsy piece of colored plastic is going to do wonders is false advertising and a poor understanding of the physics at play.
There's obviously no bounce back. But silicone padding acting like a micro-cushion will mitigate the fall way better than any 1/16" hard piece of plastic ever will.
As far as I can tell, when you open a brand new boxed MacBook Pro, it doesn't come wrapped in a hard plastic box to prevent damage from transit. And if that's the case, I surely didn't get the memo.