i prefer S phones so i upgraded - but there are things i prefer about the 5S.
the design is better - don't care how old it is, it still looks way better than the 6/6S. the size is better in my hand - i have smaller hands, so using the 6S is really stretching out my fingers.
Everyone says the cameras on iphones are so good, but my 5S is just as good as the 6S - a bit dissapointed in that. but with a 1 year old in the house, the live photos are awesome, so that makes up for the mediocre photo quality.
I'll upgrade again in 2 years to the 7S.. 😀
on a side note, i bought my 5S second hand about a year ago for $450, and I sold it this month for $400.... $50 for a year of iphone use (albeit 1 year behind the latest) is pretty reasonable.