interesting question and the science nerds will tell you a million things
a lot of guys are allergic to egg whites believe it or not, they just don't know it. in any event I eat the whole egg myself, some guys will say "no you should only eat the white"... i know a couple who are huge into fitness and 1 says yolk good, 1 says yolk bad. so really it boils down to individual opinion. obviously yolk contains more fats, calories than the whites.. seems to me like it would depend on your goal.. if you want to get as lean as possible then just do the whites.