When I had my iPhone 5, I got the 32GB model, and I never came close to filling it up. I took tons of pictures and videos, but I only kept maybe 1 movie on it, and all the social media apps and rarely any mobile games. But if you are the hardcore user, and I mean HARDCORE like, wanting to have 10 movies on your phone, 15,000 songs, etc, I think the 128GB model would be ok.

Thanks,
mobile phones sim free