MediaTek Helio X20 Advantages
Lower TDP (5W vs 6W)
Qualcomm Snapdragon 855 Advantages
Better graphics card performance FLOPS (0.8985 TFLOPS vs 0.0998 TFLOPS )
Larger memory bandwidth (34.13GB/s vs 12.8GB/s)
Higher Frequency (2840MHz vs 2100MHz)
More modern manufacturing process (7nm vs 20nm)
Released 3 years and 7 months late