the 5 cpu is "twice as fast" as the 4s and it has lte, and while still small, the screen is the aspect ratio is should have been from the beginning. also, while it is still the same pixels per inch, now that the touch layer and the screen are in one fused layer, the color and over quality of the image is noticeably improved over the 4 and 4s.
also, the 5 will open up all the new ios features in the next releases where they may start start dropping off features like they have done in the past for all other non current devices.
I did an in store test on my 4 and the 5 and the 5 was so much faster it was scary. if you are getting the 4s for $99 usd, and the 5 is $199, there is no comparision in my book, get the 5.
dont for get about the new connector and the need for adapters possibly. they are going to add up quick at $19usd each!
good luck!