As some other people have said, I like the ones where you can scan with your own device or a handheld one they provide. However, I don’t mind the regular ones where you scan everything at checkout either, though that’s definitely easier given that I live alone and in walking distance, so I don’t need to buy that many things at once. I should note that I mostly saw the scan as you go types in Europe, though a Metro store in Canada also had the portable scanners.