As a user of the 6+, 6s+, 7 Plus, 8 Plus, iPhone X, XS Max and now the iPhone Xʀ... I honestly prefer the 6.1” of the iPhone Xʀ. My X I have had since November 7th of last year. The XS Max I bought launch weekend in 2018. The iPhone Xʀ I bought the weekend after launch.
Since getting the Xʀ I have not used my Max one day. I have stayed with the Xʀ since November and don’t plan on using the Max anymore. To me after using the Max and Xʀ the regular sized X and XS feel small.
With all of this said. Over the past 5 years I have used EVERY iPhone model Apple has released. I do mean EVERYONE. I went from the 4S to the 5C to the 5S. After that I originally bought the regular iPhone 6 and then ended up using the 6 Plus instead. The 6S release was a little bit weirder. I bout the Plus model at first then went to a regular 6s until the 7 came. When the 7 came I used the 7 Plus for pretty much that entire year. I used the regular 7 at times when I wanted something smaller, but the iPhone 7 Plus was truly the best iPhone Apple released in 2016. In 2017 I used the regular 8 and 8 Plus until the X came. When the X came I used it up until I got my Max.
That said, I do believe the 6.1” screen is my sweet spot. I’m one of those people who likes to switch my SIM to different phones VERY OFTEN. I have not yet wanted to switch out of the Xʀ since I bought the phone.