8bg Iphone 4s or 16gb Iphone 5C?

[Maddi]

I have the opportunity to get any new Iphone I want, and my best options are the ones listed above. I can get the 8gb 4S for free, or the 16gb 5C for $100. (I am not up for an upgrade, btw.)
I am unsure if 8gb more storage and a longer screen is worth $100.
The most songs I've ever had on an mp3 player is about 400, and I doubt I'll ever exceed 700. I don't ever watch movies or T.V., shows, nor do I take video (I have a camera for that). I save quite a few photos from screenshots, though I don't know how much space that takes up. I don't usually download apps that take up that much space, and the biggest one on my current phone is less than 30 MB.
I use Instagram, Facebook, Twitter, and Vine, and those can take up quite a bit.
I have around $60-70 saved up in 'allowance' so I'd have to save some more. If I went with the free phone, I could save and get a lifeproof case, or some other good protective case.

So I basically want to know is it worth it to go for the 16gb? And what all could I do with an 8gb, or would I run out of space?
Thanks a ton!

P.S., I have Verizon, if that helps?