I've always wondered, if Samsung is the manufacturer, what prevents them from steal and copying this technology? Why doesn't Apple use a non-competitor like maybe Sharp?
Don't believe what others are saying... This is
not designed by Apple. This is nothing like CPU fab... Note Displaymate only credited Apple with an excellent calibration not design. This screen technology and design is completely Samsung and along the path they have always developed the best screens on the market, Apple is simply a client that set specific requirements and paid for it.
For example the increased off angle brightness is likely due to the increased Diamond Pixel fill factor... The Diamond Pixel OLED layout and tech being something Samsung has done for years and has slowly been evolving. Likely the same fill factor on the much larger Note 8 would've shot it's price up a lot more. The S8 for example has a similar screen size to the iPhone X and it's $250 cheaper.
Here's a high res picture of the Note 8
http://www.displaymate.com/Diamond_40.html
and the iPhone X
http://www.displaymate.com/Diamond_41a.html
Basically Apple just paid for them to pack in their existing format a bit more. This matches the price where the iPhone X costs more than the Note 8 yet has a much smaller lower res screen.
Again Apple just paid for what Samsung already had the capabilities to do and paid for a slightly better calibration. Most of the color accuracy differences are almost outside of the range of human perception (which is likely why Samsung pays for a cheaper calibration) though Apple should get credit for putting money into that direction.
It's not a clean sweep for the iPhone X screen, most attributes are basically the same considering it's the same tech just a slightly different variation... Though the Note 8 does reach a higher peak brightness in auto-brightness in high ambient light, 1240 vs the 800 of the iPhone X, also the Note 8 has slightly less bright off angle viewing though slightly better off angle color accuracy (so you might see a drop more color distortion at off angles on the iPhone but it'll be a bit brighter).
Again read Displaymate review, this is not an Apple designed screen like a designed CPU... this is a typical Samsung designed screen that slightly leapfrogs it's own screens like they always do with an excellent Apple calibration (likely just coming down to cost there, also the Samsung screens support 4 screen modes with an Adobe RGB color space mode that the iPhone doesn't cover, that might factor into calibration costs).
Credit where it's due... the iPhone finally has the best screen on the market by buying it from Samsung and paying for a better calibration. Though it doesn't compete in the same screen size as the Note 8... that $999 iPhone X would probably jump to $1300+ in that case.