Whatever dude. People that buy the smallest phone aren't using it to watch videos in standardized video format all the time. Is the display smaller than the old Plus phones? Absolutely. Is is "quite a bit" smaller? That's up to your own judgement. But if you think the display is quite a bit smaller, then you must think the Plus phone body is massively larger. Just look at the picture.Wrong. The 8 plus has an even greater usable surface area than the 5.8 inch models. 12.96 sq inches vs 12.7, and that surface area for the 5.8 inch models goes down to 10.93 sq inches when watching videos in a standardized video format. The mini is 10.8 inches, not much larger than the 4.7 inch phones at 9.63 sq inches. A big difference considering "only" a .1 difference in diagonal height.
Personally, I'll take the 'quite a bit smaller' display on the Mini in exchange for the massively smaller body. I have to deal with size of the phone in my pocket all the time. I only have to deal with the display while using the phone and I don't live on my phone.