What's the difference between iPhone 4s.5.5s etc?

I want to buy an iPhone but only want it for internet browsing, calls and texts. Should I save my money and go for the 4s or pay a lot more for the 5 range? What is the real difference and are they overpriced?

The name

The only real difference is the Name and the Iphone 5s runs 1OS7 which to me I think looks really stupid. Apart from that they really just do the same thing.

No they are not overpriced.

Simple answer: they have gotten lighter, faster & more powerful among them, but if you usage is minimal could get the 4s.