Minor rant time:
Plastic is cheap and light, so there's this notion that it must be lower quality. That's really not true, though. It's become really trendy to make phone shells out of exotic materials like metal or even glass, but this is done purely for aesthetics. They've become fashion accessories, basically. But the notion that these phones are somehow more durable than boring old polycarbonate is totally unfounded. In fact if anything they're less durable. If you want to avoid damage to the expensive internal components of the phone then you want something with a little bit of flex in it to absorb the impact rather than something rigid. Heavier materials also mean the phone will hit the ground harder if you drop it.
In short, plastic is fucking awesome.
Edit: I should note that I was talking about avoiding catastrophic damage. Unfortunately plastic is more vulnerable than a lot of materials to minor dings and scratches. That also contributes to its perception of being low quality. However that sort of damage should in no way impede your ability to use the device.