Foyles versus Blackwells
By Blackwells, of course, I mean the one on Broad Street in Oxford. When I moved to Oxford in 1995, they had a computing-books section that was subject-organised, with a strong slant toward books with a scholarly bent. It was a treasure trove, really, and immensely more convenient than going to Foyles. And you could buy books by taking to a till and paying the amount they asked and then leaving with the book. (Ordering books that weren't available on the shelves required you to be an adventurous soul, and was generally better done down the road at Waterstones/Dillons.)
Sadly, as the years progressed, the selection became progressively more mainstream and less scholarly in nature, probably due to competitive pressure from Waterstones/Dillons and (later) from Borders as well.