A friend of mine is in the market for a new phone. "Should I buy the new iPhone?" he asked "or is the iPhone 4S good enough?".
I'll jump straight to the answer and THEN explain a little why. This won't be a comprehensive explanation because although I am a hard core technologist, I specifically wanted to write a recommendation for those that aren't. This is specifically for people who know me and trust my judgement.
1st place goes to the iPhone 5.
Buy this phone if you want the best phone there is, because this is it. If the cost difference doesn't seem like a large amount to you, then this is the one to get, you'll love it. It IS a significant improvement in every respect over the iPone 4S.
2nd the iPhone 4S.
This is an amazing phone and the software on it will be the same (when updated) to the iPhone 5. If you're keeping costs in check and want an amazing phone, get this one.
A little note about Android phones here. Android is good. So good in fact that you would be forgiven for thinking it's as good as the iPhone, that is if you hadn't experienced them both. I have an Android phone and I'm impressed. I am also changing to and iPhone as soon as possible. For the minimal cost difference and the substantial advantages of an iPhone (from measurable features to software quality), it's not worth saving pennies and getting an inferior product. I found out the hard way. My android phone is a great phone, much better than my last, but the OS on my iPad is far superior in every imaginable way with "killer app" features, much more (and on the whole better) apps and much better security - iOS is the best choice. If you really are budget restricted to the point you HAVE to buy an android phone, don't worry you will get a hell of a phone.
... back to the iPhone.
The iPhone 5:
At a quick glance it may not seem like the big changes that we have come to expect from Apple, but when you dealing with technology that small and you making every aspect of it significantly better, this is an amazing piece of technology and a significant improvement over the iPhone 4S in every respect. Faster, bigger screen, lighter, thinner, high speed connection etc what more could you expect from something that was already so good? You want the best this is it and it's well worth it.
The iPhone 4S:
If you want to save a few bucks and still get something amazing now is your chance to snap up an iPhone 4S. The new iPhone 5 is ushering in a price drop for the iPhone 4S. So, the iPhone 4S is better for those who:
Want a better price
Don't need the extra screen size specifically
Aren't likely to use all the features of the phone
Live in a Country without a modern 4G network
The iPhone 4S is still an amazing phone, just as it was when it was released.
One last thing, generally speaking the latest phone is the one with the best camera, as the camera function is often one of the most useful things about a mobile phone this alone might be enough of a reason for you to buy the iPhone 5. Consider that carefully. For me, the mobile phone has become the digital camera of choice for taking shots of my life and family and considering it's not the only improvement on the phone, this might be one strong reason to buy the iPhone 5.
When you buy your iPhone 5 or iPhone 4S make sure you go to the Apple store (if you have one in your area) and get it configured with iCloud so that all your contacts and important information can be sycronised with your other devices and you will never lose your information, even if you loose your phone.