4K vs. 8K: Samsung Q90 vs Q900 | What's the difference?

I'm a fan of Samsung's monster 82-inch Q900 8K TV, and I might even try to make a case for the 75-inch version. But does the world need a 65-inch 8K TV? Will that question even matter in 4 more years? We pit Samsung's 65-inch Q90R 4K TV against a 65-inch Q900 8K TV to see what, if any, differences could be seen.