My thoughts are from personal experience of both the XR and XS Max which i own both of them
The XR is an amazing phone and the spec sheets are a bit misleading in everyday use, the liquid retina display is amazing and to be honest when they are side by side you really can't tell that much between them apart from the bezels being larger on the XR, but it soon becomes a distant memory after using the XR for a few days.
Yes the XS has an oled panel, and it looks amazing, i'm 48yrs old and my eyesight is no longer perfect with seeing the finer detail that the oled has to offer, and from 9-12" away they look very similar.... you really need to look at it with a certain coloured background/text to see the difference IMHO.
good luck with your decision, i'm still sat here with two phones and each day i change my mind which one im going to keep lol
One final point the XR has amazing battery life, i get half a day more than i do on my XS Max, probably due to the different screens requiring different levels of power...