Qualcomm Snapdragon 821 Advantages
Better graphics card performance FLOPS (0.3343 TFLOPS vs 0.2362 TFLOPS )
Higher Frequency (2342MHz vs 2270MHz)
HiSilicon Kirin 810 Advantages
Larger memory bandwidth (31.78GB/s vs 29.8GB/s)
More modern manufacturing process (7nm vs 14nm)
Lower TDP (5W vs 11W)
Released 2 years and 10 months late