That "normal viewing distance" myth only works in reverse gear, that is, when there's nothing worth seeing up close. Otherwise, a richly
detailed print will draw people in, regardless of how big it is. But the point is not what is "correct" to do, but what do you want to do, and
how well do you do it. Since I shoot every format from 35mm to 8x10 I get to know the distinctions pretty well. Smaller formats give you
more portability and spontaneity, while large formats give you more surface area with more visual information, as well as a different approach to looking at the world. I'd far rather make a 16x20 print from an 8x10 negs than from 4x5 than from 6x7. But if 6x7 is what bagged the shot, I'll sure as heck do my best in the darkroom to make that little Dachshund mutt of a negative pretend it's a Rottweiler!