The stated Constrast Ratio of Samsung (and everybody else, for that matter) is, well, BULLSH*T!.
A normal "white" brightness that you are likely to view is 120 nits... lots more than that is the same as a bright light shined into your eyes.
IF, and a BIG IF, the darkest black were .30 nits... the Contrast Ratio you'd view is 400.
Unless you run your computer in a dark closet, you're unlikely to EVER actually see a CR = 500.
Pick your monitor on something other than CR.
CR aside, both are good for gaming.