I was watching a vid on YouTube, this one to be exact:
,and was actually surprised that there is actually no benefit to the bigger size of the XS Max.
Both the XS and XS Max show the same exact amount of information on the screen (i.e if you are in the same app on both devices, for example - twitter, both devices will show the same exact number of tweets).
I would have thought that with the bigger screen of the XS, you would get to see more information but clearly this is not the case. The XS Max just displays the same info as the XS but in a bigger format.
If you watch that vid - you'll see that both devices are in fact about 99% the same.