Yup, that was the iPhone 6 screen. If Jony Ive’s dream of a glass slab would come true, a phone of that size (under 7mm thickness by the way) with a bezeless display would have been at around 5-5.5 inch. That’s what phones should be like now instead of horrible camera bumps and notches.
I will say I got to handle a galaxy fold 4 and if a screen has to be bigger, I don't mind as much as long as it's narrow like that phone. I was still able to one-hand it comfortably.
The idea of "best" for something that people have different preferences about makes little sense.
I'd like under 5.5" on a modern design with minimal bezels resulting in a device no larger than the Nexus 5. The fact that nobody's selling such a phone makes me think most people prefer something else. Everything is huge now, but some are huger than others, demonstrating there's still a range of preferences.
Again people, diagonals without aspect ratio is pointless, because there's a lot of variation on the sizes.
I think mine is 6" 16:9. The Galaxy Note 3 at 5.7" 16:9 was pretty damn close to my ideal. I still find phones a bit too small (read: narrow) for my liking.
Best one? I wish phones under 6" and more close to veing just 5" were still a thing, so it fits pockets nicely and I CAN TOUCH THE OPPOSING DIAGONAL EDGE WITH MY THUMB