Samsung Exynos 7870 Advantages
Lower TDP (3W vs 9W)
Samsung Exynos 990 Advantages
Better graphics card performance FLOPS (1.126 TFLOPS vs 0.0224 TFLOPS )
Higher Frequency (2730MHz vs 1600MHz)
More modern manufacturing process (7nm vs 14nm)
Released 3 years and 8 months late