I've never met you in person Jack but I've enjoyed reading your writings for several years. If we were talking guns and you used the term "bore", I probably wouldn't notice. If I did notice, it would be the farthest thing from my mind to think you pretentious. Pretentiousness is an overall behavioral pattern, and as we all know, its easily detected in person and pretty much held in universal distain. I just think that using "bore/gauge" to label the intentions of a person on either side of the Atlantic is a bit of a stretch. And, like you said, if they enjoy using one or the other, who are we to judge?
Here's a question.......is it pretentious to use an English Cocker to hunt American birds in America when we have our own perfectly good American Cocker? ;-)