IPhone 6s (16 GB) or iPhone 6 (64 GB)?

It, s going to be my first apple product so have heard from several people that i would give on a small space but i have enough money that i can even buy a 6s but with only 16 GB.
On android i stored 400 songs & most of the pictures had i upload on social media but delete on my phone so out of 8 GB on android i used around 6 and in SD card out of 8 i used around 3 or 4 Gb, s.
But i also want a better technology like 6S so what should i buy?

IPhone is 6s is far better than iPhone 6 as iPhone 6s comes with a lot of new feature like 3D Touch, 2GB RAM, 12 MP camera and a lots more.
As storage is also a think of concern. It depends upon on your usage of smartphone. If you are a light user a bunch of apps and services then you should go with 6s. If you are a gamer then storage is a headache for you. Then you grab a heavier storage.