Qualcomm Snapdragon 820 Advantages
Better graphics card performance FLOPS (0.3194 TFLOPS vs 0.1843 TFLOPS )
Larger memory bandwidth (29.8GB/s vs 5.3GB/s)
Higher Frequency (2150MHz vs 1800MHz)
Qualcomm Snapdragon 636 Advantages
Lower TDP (5W vs 11W)
Released 1 years and 11 months late