Well i have the Case-Mate Tough Case on my Galaxy S which is a two piece case and now i have the Otterbox Impact case on my Streak which is a one piece case and i much prefer the Otterbox case. I think its of better quality and the buttons are much easier to use then with the Case-Mate case plus of course I'm using the Otterbox case now as opposed to waiting for Case-Mate to even release theirs and the larger case for the Streak was cheaper then the Case-Mate case for the Galaxy S to.
Samsung Galaxy S3 Pebble Blue 16gb, Rom Super Nexus JB 4.1.2 Build5
Motorola Xoom UK ICS 4.0.4 32gb 3G +32gb SD Card
The only problem with common sense is that it's just not that common.