I hope my lcd screen comment didn't start any negative vibes.
Looks can be rather deceiving though. My dorm mate sold his 9300 and bought an MSI 1029 and even though the MSI is rather bulky looking and has this rubber look and texture all around it, the laptop itself is less sturdier than my z70va. We did a test with the middle of the lid and when barely pushed, his lid would flex inward. I can push on mine and the whole screen starts coming down. I can't comment too much about the 9300 because I haven't really used it but from holding it a few times I can say most of the sturdy feeling comes from its inherent thickness.
A book with thick covers will feel much sturdier than a book with thin covers and thinner things tend to flex much more, so it is a tradeoff. For being this thin, the z70va is good at not flexing madly. However it does flex a little here and there and mine creaks a bit, especially when holding around the sides. Carbon fiber isn't everything and not at all revolutionary. I would say the 9300 and z70va might be equal as thin carbon fiber = thick plastic, don't you agree?