This is not about which camera is worse than the other on itself. Were talking about what about the cameras on the X that are better than the 8 and 8+.
No matter how you cut it with your red herring fallacies... the front camera of the iPhone X has Portrait Mode for more professional looking portraits, and the bigger and better screen makes a bigger and better viewfinder. You cannot deny that.
The original post asked if there are any differences between the 8 Plus and the X camera, and since this thread was about video and specifically 4K, the front camera is irrelevant. This wasn't asking for the complete differences between the X and the Plus. Also, the 8 Plus has pretty much the same viewfinder since the screen is about the same, slightly shorter but thicker than the X.
https://www.iphonetricks.org/iphone-x-iphone-8-and-iphone-8-plus-screen-comparison/