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Ios6 can stream with iTunes match rather then download it to the device so you should be fine with 16.
 
I've got iTunes Match and use Spotify. I have now between 17GB and 18GB free on my 32.
I do have a couple of large games and nav apps on there.

Unless you have nothing else on your phone, the 32GB would be future proof (and also if you want to create some movies in 1080p)

How much space do you have now? If you don't see yourself adding to it much, then go 16GB.
 
I use Match and got a 32 this year because 64 was too much for me on my 4S. 16 may cut it close if you have a lot apps installed.
 
I have 8.4GB left on my 4S 16GB right now. And doesn't steaming use up data lol? I have that sexy limited 3GB AT&T data..
 
Yes, it does. You can download your favs over Wi-Fi and keep them on the phone.
 
Another thought, is that I use retired iPhones as iPods. Thus I preordered the 64 gb, which will hold my entire music library. 32 gb won't. So two years from now when my iPhone 5 retires to iPod duty, I'm good to go.
 
Another thought, is that I use retired iPhones as iPods. Thus I preordered the 64 gb, which will hold my entire music library. 32 gb won't. So two years from now when my iPhone 5 retires to iPod duty, I'm good to go.

Nothing in your post applies here since we are discussing using iTunes Match, which provides your ENTIRE library to you without taking up much space.
 
16 GB is more than enough for me now that I have my iPad. It would have been cutting it too close when I didn't have the iPad and when I used TomTom pre-iOS 6. I have a 32 GB 4S but couldn't justify it this time based on my usage.
 
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