Is there much difference between the iPhone 4s and iPhone 5?

I've never owned an iPhone before. I've got a crappy little HTC Wildfire S at the moment that I really need to get rid off. I found a really good 24-month contract offer for the iPhone 4s on vodafone (300 minutes, unlimited texts, 250mb + 2GB Wi-Fi & iPhone for free) and I'm tempted to do it. From my own research there doesn't seem to be that many differences between the 4s and 5, except the obvious (slightly faster processor + bigger screen)
I actually prefer the design of the 4s/4, especially the back.

Owners of both the iPhone 4s and iPhone 5, what do you think?

I think it is down to personal perfereance. The 5 is slightly more evolved and bigger than the 4.It also has a few new features ect- that you would use around 1% of the time. If you want the better if two go for the 5, but bear in mind that it is not £100 better.
Aka go for the 5 if you want a phone to show off. Go for the cheaper 4 if you don't.

I own the 4S, never the iPhone 5, but my friend owns it and I'm glad that I didn't pay nearly $600 dollars for.5inches of a screen and 4G. Sure, the speed boost is great with the processor and faster data speeds, but to be honest, I never complained about the 4S being slow whatsoever. The best part is that it doesn't even come with a better camera, only with a special lens that makes the pictures look a little bit better at best. This was a mediocre attempt at recreating the iPhone and I'm glad I'm staying with the 4S. Funny thing by the way, someone the other day say my iPhone and asked me if I had the 5! Lol.

You're going to be stuck in a 2 year contract, so in 2 years from now, consider that the Iphone 4s will be 3 years old by then. There's some major differences between the 4s and 5. The screen on the 5 is larger but also the processor is on the Iphone 5 is more efficient while offering more power. While you might notice the performance difference, the battery life on the 5 is going to be noticeably better.

Chances are, unless you're a phone-geek you won't notice a huge difference and you can't go wrong with a free Iphone. Enjoy!