Can I use my sim card from iPhone 4 to use in iPhone 5?

I'm thinking about getting either IPhone 4s or I phone 5. Can I use my sim card from old phone to new one? Is iPhone 5better then 4s?

You need to get it cut to a 'nano sim' for the 5, the 4S is still the micro so it would work.

You need to either cut your micro sim (not recommended easily can be done wrong) or just get a nano-sim from your wireless company

as for the iPhone 5 being better, yes:
larger display, better battery, thinner, faster.

No, the iPhone 5 is one of the first phones to use a nano-sim. The iPhone 4 used a micro-sim, and the iPhone 5 is not compatible with this. Visit your carrier or call them and they should give you a new one.