When I first installed iOS 10 I had major lag, slowdowns, glitches and a crash that I had to go pay $30 to get it fixed and unjammed at an electronics place.
So until the next update came out I used my blackberry 9900.
Now iOS 10.1.1 fixed everything, my 5C is fast and amazing as it was when it came shipped with iOS 7. I was actually going to get an iPhone SE but I'm sticking with the 5C for now.
No problems whatsoever. Just installed battery doctor that allows you to clean the cache and on my 16 GB 5C I actually have seven gigs free and Thats with 45 apps on my and over 200 photos. That's pretty amazing so I have no reason to switch.
I realize I might be taking a chance with an older device and that many apps and risking a jam again (remember the issue was iOS 10 being full of glitches IF you have a lot of apps) but I'm testing and pushing this thing to the max! And iOS 10.1.1 is a godsend.