Difference between dynamic contrast ratio

[HDMI703]

80M:1 vs 20M:1 Dynamic Contrast Ratio, Which one is better ??

 

[USAFRet]

80M:1 vs 20M:1 Dynamic Contrast Ratio, Which one is better ??

In a perfect world, the 80M:1.
In the real world, either. Those are marketing numbers. There is no 'standard' for measuring this.