The main difference between the Kirin 810 chip and the 820 chip is performance and power consumption. The Kirin 810 chip will have worse performance than the 820 chip, but lower power consumption, while the Kirin 820 chip will have better performance, but also higher power consumption.
The Kirin 820 chip is an upgraded version of the Kirin 810 chip, which has been improved in terms of performance and speed