How many GB's do I need on my iPhone?

Hi, I'm finally eligible to upgrade my phone and I'm going to get either an iPhone 4s or 5 but I have no idea how many GB's to get!
My friend only has 8GB and she has to have a separate iPod to put her music on, but I'd prefer to just have it all on my phone to be honest.
I have about 700-800 songs, and I'd also have quite a few apps on my phone, so do you think it would be better to get 16GB or 32GB?
Also, any opinions about whether I should get the iPhone 4s or 5 would be appreciated!

I would say get 32, because if you already have a bunh of music and apps, and you might want to download more, or load on more music. Also, i would say iphone 5 because it is the newest, and will stay recent and compatible for longer.