Rene Ritchie, writing for iMore:
Conversely, Apple’s silicon team also doesn’t have to carry the
baggage of competing vendors and devices. For example, Apple A10
doesn’t have to support Microsoft’s Direct X. It only and exactly
has to support Apple’s specific technologies and implementations.
In other words, what iOS wants fast, the A-team can deliver fast.
I’ve said it before and will say it again: I’d prefer the iPhone over Android even if it were Android that had the massive lead in CPU performance. But Apple is literally over a year ahead of the competition — even the iPhone 6S and SE outperform the S8 in single-threaded performance.