Yes, it definitely has to have the right dynamics. Shape, firmness, curvature.
The ass is a group of MUSCLES. It shouldn't be rock hard, but definitely firm. Feeling on a nice ass...DAMN!! That's a beautiful feeling.
In complete contrast, the big, super soft, 'squishy' ass....ummm, I'm going to have to say no to that.
Again, it's a MUSCLE, and muscles are supposed to have some development to them to truly be the best muscle they can be. The cottage cheese look, uhh, not really ideal. A little of it isn't always bad, but ladies should STRIVE to have a nice package back there.