I didn't know about this. I did my own mini, completely non-scientific test since I have a Note 8 and an iPhone X. I watched an episode of Stranger Things in HDR on both, side-by-side last night and the iPhone X blew me away. It was incredible. I was surprised that it did better than the Note to be honest. I'm wondering if it has anything to do with the fact that Apple implemented Dolby Vision HDR and Samsung uses HDR 10. It is my understanding that the two standards are encoded differently. But as it stands now, even though the Note 8 screen is bigger, I'm finding that I like the iPhone X display better overall.
I would imagine being released 2 months after the Note might help with that. Still not worth the extra $.