Qualcomm Snapdragon 439 Advantages
Lower TDP (5W vs 6W)
Qualcomm Snapdragon 678 Advantages
Better graphics card performance FLOPS (0.3244 TFLOPS vs 0.0432 TFLOPS )
Larger memory bandwidth (14.9GB/s vs 6.4GB/s)
Higher Frequency (2200MHz vs 2000MHz)
More modern manufacturing process (11nm vs 12nm)
Released 2 years and 6 months late