I don’t know about speeds, but driving through the middle of nothing out in the middle of nowhere my husband’s XS Max was consistently getting only 1-4 bars of 4G while my Xr was pulling in 1-4 bars of LTE on AT&T. Quite often I had 2 bars of LTE when his Max had only one bar of 4G. Nevertheless his phone streamed music flawlessly and my Xr did great pulling down web pages.
In real life, I am very happy with the Xr so far. Call quality has sounded good so far, too.
I forgot to add that having said all that, I would be happy for iPhone XS owners to have modem speeds that crush mine. They’re paying through the nose for that performance, after all. I hope they get it. I know when I bought my Max I was hoping for mad modem performance. I’m disappointed I had problems with the display and had to return it. And I appreciate that I can use the excellent Xr. But I also appreciate that I got some significant cost savings going with the Xr. I don’t begrudge any superior modem performance to the premium priced models.