In the 2.5 weeks of owning the iPhone Xs Max, today was the first time I've had the phone stutter and drop out during a phone call (AT&T), and it was in my typically low signal neighborhood when I was driving up to my house but still too far away to connect to WiFi calling.
However, I was hoping that the Xs Max would improve upon the poor reception we always get on Cheyenne Mountain with all of our previous AT&T (and Verizon before that) cell phones. Not even re-connecting my Micro-Cell that we got 10-12 years ago would have helped.
With my iPhone X I was in the habit of just leaving LTE turned off all the time, as it was quite as good as my iPhone 7+, so that I didn't lose calls when walking down the street with the dog. I have not had to turn off LTE to keep cell service with the Xs Max yet.
I'll have to hope for next year, because it's no worse than my current unlocked Qualcomm iPhone X on another line, nor my wife's iPhone 7 (and the 7+ I gave to my brother 2 weeks ago). I wont switch to Android, I'm too invested in the Apple ecosystem.