As a "senior" myself, having passed the 73-year-old mark, I'll speak up here...... Last year I bought the iPhone X and this year I bought the iPhone XS. I LOVE Face ID, which works so much better and more responsively than Touch ID ever did for me. I also do not miss the home button at all. Swiping up becomes instinctive and natural very, very quickly. Just because someone is older does not mean that they are unable to adapt to new things or to learn new things.....unless the individual in question is struggling with cognitive issues such as the onset of dementia.
Someone doesn't need to be especially "techie"-oriented in order to use the iPhone X, XS or XR. (Disclaimer here, though: as it happens, I am rather "techie" and have been using computers and various devices since the mid-1980's, bought the iPhone the day it was launched in 2007, bought the iPad the day it was launched in 2010, etc., etc.) I have friends who are not especially interested in exactly how their devices work, just so the things do whatever the user wants and needs, and occasionally I'll get a call or a text -- "help!" -- about some issue or other, but for the most part they do just fine with their iPhones, iPads or computers.
I agree with the suggestion that if possible, you take the person to the store with you and let her choose what feels best to her.......
