4/3 is 1.33:1, the same as Silent Movies and Standard Definition television. 4X5 is 1.25:1. A magazine page is about 1.3:1, so either 4/3 or 4x5 is a good size, unless you are shooting for a 2 page spread (double truck) which is about 3x2. I like 1:1 for Portraits or Fine Art, but I don't shoot either. Although I'll sometime crop 1:1 to get rid of an unsightly background for my personal work. Life would be so much easier if one size did fit all. Well, I guess we could go back to 6x6 Film, and crop after the fact. 8-)