iPhones are the only device sold by Apple that are only rated for 500 charge cycles before degradation starts. Macbook, iPads and Apple Watches are rated for 1000 cycles. In the case of the Apple Watch I'd guess it's because despite being tiny, the SOC also doesn't ask for as much peak voltage as the phone SOC.
I've had the Honor 8 for a year. It's still holding a great amount of charge and running fine and as fast as the day I bought it. And unlike my 5s, no phone update is coming to turn it into a slow crawl.
The iPhone battery problem with regards to the topic, spontaneous shutdown at 30% and less battery remaining, is probably exacerbated since the evolutions that made those SOC more powerful than before. There wasn't a large wave of 5s owners having spontaneous shutdown requiring an OS update to throttle the CPU. That only started with the iPhone 6. A combination of paltry battery and modern SOCs having peak power usage that stress such battery more than before.
