Qualcomm Snapdragon 821 Advantages
Better graphics card performance FLOPS (0.3343 TFLOPS vs 0.0918 TFLOPS )
Larger memory bandwidth (29.8GB/s vs 11.9GB/s)
Higher Frequency (2342MHz vs 2200MHz)
Samsung Exynos 9609 Advantages
More modern manufacturing process (10nm vs 14nm)
Lower TDP (9W vs 11W)
Released 2 years and 9 months late