depends on the girls body
side boob you can only see one boob, underboob you can see both
BUT side boob you can also see the butt...and you can't do that with under boob
so it's clearly dependent on the girl
I love looking at my wifes tits from the side. She has HUGE nipples (asian thing) and they really look the best from the side. I won't pass on a underboob view either. 11 years with her and I still get reved everytime I see her naked. Life is good!