What's the difference between an iPhone 3GS and an iPhone 4?

I'm on verizon and I currently have a Droid Incredible. I want to switch to an iPhone. I can get an iPhone 3GS very cheap and in good condition. I just want to know what and if there are any major differences between the iPhone 4 and the iPhone 3GS.What's the difference between an iPhone 3GS and an iPhone 4?the major difference is speed and appearance ...Iphone 4 is thinner and looks a little better....Iphone 4 is also faster and has a better quality screen...What's the difference between an iPhone 3GS and an iPhone 4?Check out http://www.apple.com/iphone/compare-ipho鈥?/a> - they have the exact differences between the 2 phonesWhat's the difference between an iPhone 3GS and an iPhone 4?the iphone 4 is way better the camera like quality everything is so much better i love it...