Quick charge is a game changer. Less pressure to make the battery bigger if you can make the phone charge way faster.
For me, USB-C is the worst part. Nobody else ever has a charger I can use, and when I plug into anything other than the wall adapter that came with the phone, it's always "charging slowly."
https://www.amazon.com/adapter-Adapter-Convert-Connector-One...
Isnt it [0]? A 10-100% gain in performance is about what I'd expect from a 2-year smartphone cycle, and we'd be lucky to continue to get such gains.
If you can present data that actually shows no performance difference between the 5 and 5X, I'd be interested to see it.
[0] http://arstechnica.com/gadgets/2015/10/nexus-5x-and-nexus-6p...
Also, 5X uses the USB-C connector, so you have to update all your cables and adapters on your desk and in your car. A real pain. When you're out in the world and need a charge-up, you'd better be carrying a USB-C cable, because no one else will have one.
I consider the 5X a side-grade and not of any particular value if you already have a 5. The 6P is at least a larger handset with a larger battery so it's got that going for it.
You do have to remember to collect them when you're done, but the penalty for forgetting every now and then is not ruinous.
(Local distributor here has a minimum 1.5x markup plus a very very limited range)
But being able to simply set my phone on my desk and keep it fully charged is a convenience I won't soon give up. I now buy phones with that in mind.
In theory, plugging in a cable isn't time consuming, but in practice, I only actually keep my phone charged during the day if I have a wireless charger nearby.
YMMV.