Iphone 6s 16 gb or iphone 6 64 gb?

They are both £539.00 and I was wondering whether a 16 gb phone would be too small, also is the pros of the 6s would make up for the limited storage?
I'm upgrading from an 8gb ipod, which has finally died after almost five years of use. I ran out of storage very quickly due to my music library and photos using around 4gb of storage, so had very little apps and it was slow and I do not want to pay over £500 just to have it run out so is there a considerable difference between 8gb and 16gb?

64GB

16gb please very few people actually need 64