Harder? Wow, do you throw your backpack around a lot or something?
The Marware case has hard plastic wrapped in neoprene around all the edges so when your MacBook Pro is in your backpack and you set it down roughly, the edges of your MacBook are protected from damage. My gf has told me time and time again how much she likes this feature; it especially comes in handy when she sets her backpack down on a park bench. The hard plastic keeps rivets like the ones found on park benches from denting your laptop.
I can't recommend these cases enough. A "harder" case won't protect your laptop in a backpack any more than the Marware or any other softsided case will. When you set down your backpack, only the bottom edge of your laptop case will come in contact with that surface.
Also, a harder case will be extremely thick and take up lots of room in your backpack.