I had the iphone and used silicone case for it. I find that hard cases scratches my phone. The first case I purchased for my iphone was an incase, the one where you can push back to insert charger, but after I used it for a week, I found scratches on it and refund it.
The otter defender is a hard case with a rubber outer skin. My DH has one and it's been superperfect! He used to have a soft rubber case and that lasted about 2 months. He's had the otter for over a year and it's still like new!
I had that problem too. I had my phone in a hard case, and sure enough, fine scratches on the back and even the chrome. No more hard cases for me! I'm paranoid about scratches because when the new version comes out, I'll be selling the phone, so I want it as pretty as possible. Currently, I have an Invisible Shield on the front and back. I dropped the phone accidently, and no scratches, even on the film itself.
I have a gel case. It's not as hard as a hardcase but there won't be cracks if I drop it. I don't like silicone cases just cause it attracts a lot of dust and hair.
The invisible shield is a wonderful protection for the phone as it prevents it from key scratches also. But I had a friend who used it for her first generation iphone, the shield turned yellow over time.