I have the iPhone 5 and a lot of people told me it freezes up a lot and isn't worth buying but I've had it for over 2 months and has not froze up once and it has a great camera and battery life. I only charge my phone once a day. And this fall they are coming out with iOS 7 and it's supposed to totally change the layout of the phone. In my opinion it is worth it. And if you already have an apple i.d. which I'm sure you do since you already have an iPhone then you won't need to use a credit card. I just used my same apple I.d. and didn't need a credit card. I also really like the charger I used to struggle plugging my old iPhone in at night because you have to plug it in on a certain side but with this charger you can plug it in either side.
I have the iPhone 5. Something you may not know about this phone is a credit card is a mandatory attachment to this phone. It operates fine, I would have chose I different phone if I had the opportunity again.
Although the two iPhones have a lot of similarities, the iPhone 5 offers 4G LTE cellular networking, while the iPhone 4s has 3G networking. If you need to have the latest phone in the market, the iPhone 5 is for you. The iPhone 5 also has a better camera and video than the iPhone 4s.
It is worth it, for it comes with a better processor and better glass. It is stronger so it won't break with a simple drop. Also you don't have to buy new headphones for they already come with the new earpods when purchased new. It doesn't freeze at all, I don't know how it would freeze. Just keep you iPhone 4, because the iPhone 5s will be coming out later this year. But if you want, it is your choice, you can get the iPhone 5.