Is is worth it to pay 100$ to get an iphone 4s instead of an iphone 4?

My husband is due for an upgrade and can get the iphone 4 for FREE or the iphone 4s for 100$?
I have heard that Siri is the only difference, but reading online it seems the 4s is a little faster and can hold more.

I'm leaning toward him getting the 4s, especially because he's gonna be gone a lot and I want facetime to work really well, however I don't know how it works on the 4s compared to the 4. I'm just wondering if you think it's worth the extra 100$ to get the iphone 4s or if he should stick with getting an iphone 4?

Any advice is greatly appreciated!

No, siri is the only real diff, and it can be put on any jailbroke iphone 3gs or 4.
they both hold the same amount of stuff if they are both the same size.
the 4s is a lil faster but the 4 has a better battery life.

No, not exactly.

The iPhone 4 and 4s aren't much different at all. You're right; the only real difference is Siri.

Also, you can just jailbreak the device and install Siri manually on the 4.

By the way; jailbreaking is free.

4S is the better choice if you plan on using it longer, but 4 is free with a year plan if you plan on upgrading in 2 years. If you don't plan on upgrading in 2 years then go 4S or I think you will wish you had gotten that.