I like building 1/48, but I like displaying 1/72.
Realistically speaking, with my eyes and coordination, 1/48 works best for my abilities. However, I really like seeing models displayed next to each other - it lends a reality of scale. Even if someone produced a 1/48 B-52 or KC-135, it would be too big to display together with F-15's, F-4's, etc, in anything but a small museum, and your eye would have a hard time viewing such large models in perspective except at a large distance. To me, 1/72 models look very nice placed side-by-side.