There are three aspects of the OP article I liked. One, Ms. Senior admitted to the snobbery charge. Second, she admitted to herself being a semi-secret downmarket reader. And, third, any urge she may have had to blame it on the malign influence of my own country -- for example, by describing the disparaged Christian fiction as American Christian fiction -- was successfully resisted.
As to whether Antonia Senior is correct, evidence for drawing our own conclusions is here:
New York Times Bestseller Lists
Comparing the eBook and paper non-fiction lists, I am having a hard time seeing any systematic difference. One can hypothesize that people who are politically conservative are more likely to buy paper. But that may be a coincidence based on just two titles that do better in paper than eBook (Ameritopia, American Sniper).
As for fiction, I'm not familiar enough with those authors to evalulate the New York Times lists. Does anyone here who would know see any systematic difference between the eBook fiction and paper fiction bestsellers?