What's the difference between the iPhone 5 and the iPhone 4S?

I really want to get an iPhone. I'm used to my iPod, so iPhone is the best choice for me. I was looking on t-mobile's website, and they seem to be pretty much the same phone, besides the 4S is a bit thicker. But is there a huge difference between the two? If there isn't a huge difference, I would rather pay 70 dollars than 146 dollars.

Your getting much more speed, battery life, better screen picture quality, and LTE if T-Moblie has it. If you buy the 4s your already one generation phone behind and the rumor is Apple is going to release a new iPhone along with a cheaper version as well. Between the 4s and the 5 though, go with the 5 because technology moves fast.