Worth the upgrade?

I have had my iPhone 4 for many years now, and it is slowing down. With the 5s out, I'm considering the upgrade, but I can only buy it unlocked, which costs $720. I don't want a contract so therefor I must buy it unlocked. I am wondering, for $720 is it really worth the upgrade from 4 to 5s? I see no major difference, I already have a MacBook Pro and iPad mini... but i feel somewhat forced to pay for this upgrade to the 5s. It seems like for $720 I could get much more than just a bigger screen and speed improvements. I do have the money but I'm not sure if it is worth it. Any thoughts on whether I should or should not upgrade?