MediaTek Helio G81 Advantages
More modern manufacturing process (12nm vs 14nm)
Released 8 years and 9 months late
Qualcomm Snapdragon 820 Advantages
Better graphics card performance FLOPS (0.3194 TFLOPS vs 0.0912 TFLOPS )
Larger memory bandwidth (29.8GB/s vs 13.41GB/s)
Higher Frequency (2150MHz vs 2000MHz)