Qualcomm Snapdragon 660 Advantages
Lower TDP (5W vs 10W)
Qualcomm Snapdragon 888 Advantages
Better graphics card performance FLOPS (1.72 TFLOPS vs 0.2176 TFLOPS )
Larger memory bandwidth (51.2GB/s vs 13.9GB/s)
Higher Frequency (2840MHz vs 2200MHz)
More modern manufacturing process (5nm vs 14nm)
Released 3 years and 7 months late