Qualcomm Snapdragon 821 Advantages
Larger memory bandwidth (29.8GB/s vs 17GB/s)
Samsung Exynos 1280 Advantages
Better graphics card performance FLOPS (0.487 TFLOPS vs 0.3343 TFLOPS )
Higher Frequency (2400MHz vs 2342MHz)
More modern manufacturing process (5nm vs 14nm)
Lower TDP (6W vs 11W)
Released 5 years and 7 months late