I have an iPhone 5 and my wife has the iPhone 4s. I just recently upgraded from the original iPhone 1, as released in 2007.
The faster CPU aside, IMHO, the 4s feels to be a higher quality phone than my 5. Also, my screen is a little longer, but the only thing that occupies that extra space is ads.
If I were in your shoes, I would go with a 4s or wait for the 5s.