Give it a rest, biased, lol. Firstly how can I be biased against more than 4GB because? I recommend against wasting money on the 8GB version of a 290x before there was ever a Fury X or a Titan X.... but don't let that stop you.
Then you yourself, you've stopped saying what games need it, just broadly stating it. You also repeatedly use a illogical argument that if you haven't seen the card physically in person you know less about it. Like your inability to understand why a core 30% larger with the same power output will run cooler, which is a basic fact, while calling Fury X a hotter running core than Hawaii... but you know better because you've physically taken the cooler off one which trumps mere physics and huge amounts of evidence.
You cited TWO games last time you actually cited games with this spurious claim, Shadows of Mordor and xcom 2, two games which have uncompressed textures of the same quality level as the compressed textures of the lower texture setting. Both are Nvidia games, which is a compete coincidence and both came out as Nvidia pushes cards with a higher price with more memory.
If there was an 8GB version of Fury X, I'd recommend the cheaper 4GB. There is a 8GB version of 290x/390, in both cases I DO recommend the cheaper 4GB version. I have told people who are convinced they will go Nvidia already to get a 980ti because the extra memory of the Titan X is worthless for gaming.
If you care anything at all about IQ, you don't need 4+ GB, if you only care about pushing every option to the max regardless of IQ difference, then you need more than 4GB but only because Nvidia have worse memory usage(they have since the x800) and they will pay devs to increase memory usage to make them look better.