Using those numbers, when an SE hit 0% after 9.27 hours of usage, the XR would be at 28.5% (12.97-9.27)/12.97. That seems reasonable and makes my original claim that an XR would be at 40% was a hit high, but in the same ballpark. There’s certainly no doubt that the SE’s battery size and power management doesn’t compare to the current phones’.
Though it's worth pointing out that the SE did beat out its contemporary iPhone 6s, with which it shares most of its innards. Differences are the smaller display, slightly smaller battery, 1st vs 2nd gen TouchID, and a lower res front-facing camera.
24% longer on wifi web browsing. Worse on the graphics benchmark, but only because the framerate is higher (smaller screen resolution) which keeps the CPU from idling as much.
Makes you wonder what the performance of a modern small iPhone could be like.
It is worth pointing out the test were using WiFI and assume best connection. In real usage the XR would get better LTE performance and hence even better battery life than what was tested.