OP proved there are 6 insecure iPhone 4S owners so far. Anything to see their own phone win in any argument. And if it doesn't win, the owners sit there and pout while thumbing down the post.
Let's be real. Glass is beautiful but this comparison is like dropping a plastic cup vs a shot glass. If everything in our house was made of glass, there would be shards everywhere. Hard plastic might seem "cheap", but it is more practical toward drops and reception.
The best build quality comes from HTC, in my opinion. They use alot of aluminum/metal along with a soft touch. Check out the build quality around the Sensation and its variations like the XE. Feels premium and sturdy. Now if only they had more responsive touchscreens, increase the speaker quality, and throw in the MyTouch Slide 4G camera quality on most of their top-end phones. Then they would be the very best Android/WP7 OEM out there. Samsung has taken their crown this year although HTC was the champ in 2010.