Which iPhone 6 storage should I get?

OK so I know I'd never use over 64GB so I definitely won't be getting the 128GB iPhone. However, I can't decide between the 64 and 16 GB phones.

I have about 5GB of music and I do like to take photos (I can store the photos on my computer though). Then I would also have some social apps (Facebook, Snapchat, Twitter etc.), as well as some other apps/games.

I already have a 32GB Nexus 7 of which I only use 10GB (17GB free space). I don't store any music on my tablet though.

What do you think?

I would definitely go for the 64GB.
Apple often bring out new updates for the operating system and they can take up space. I have a 32GB iPhone 5S and I've just had to delete a load of photos to do the latest update.
In my opinion, it's better to have too much space but be able to have all the photos, music, apps etc without worrying than having to go through and delete them when the next update comes.
Hope this helps.

16GB