What is the difference with the iphone 4 and iphone 4s?

For Christmas i'm getting the iphone 4 but i heard of the iphone 4s, what is the difference between them and are they better to get than the iphone 4? And what is the battery like on the phone.

The only difference really is Siri. IPhone 4 is great:3 iPhone 4s just happens to have Siri.

Simply the iPhone 4s comes with the Siri ability but since the new iOS update i'm pretty sure the iPhone 4 has the capability of using Siri now because they made it available for iPad but not to sure. 4s I think also has some other better features but the S stands for Siri

Siri, more ram, faster processor, better camera