While you guys make good points, I see the iPhone winning on all drop tests with the S3 & after several tests and several drops per tests. Dropping a phone is a far more common way to break it than sitting on it and the OPs comparison only tested one device. This was the only kind of real durability comparison I could find.
To be honest, I don't really care either way. Both are great phones. I just would not conclude that polycarbonate makes a phone more durable.
The only drop test that matters is when you drop your own phone by accident, if it survives unscathed, you have a winner. Don't make a habit of dropping it though, because it will eventually become a loser.