It's not a battle, because iPhone 4S is the iPhone 4's successor. But just for the fun of it, let's see the specs compared:
As you can see, Apple dropped the price on all iPhones. If the fresh iPhone 4S starts at $199, the old iPhone 4 is only $99 on contract. I have lots of friends who can afford it now! What's new? A better processor, better battery life, better camera.
I'm a little dissapointed, because I was hoping to see the iPhone 5 release, not an upgraded iPhone 4. We'll wait and see what the future holds.
Check Apple's website to see what other features were presented.