Hard to say given the nature vs. nurture debate, neither one occurs in a vacuum. Even with awesome genetics a fish may never reach it's size potential if there is too much competition and not enough forage go around. Even with bad genetics fish may grow to large sizes with a lot of forage present and little competition.
Let's pretend that everything is equal with a lot of forage and very little competition, then genetics may play some sort of role in aggressive non-choosy eating behavior where the offspring of some may fair much better than others that are less agressive more choosy eaters.
To me the answer is not clear cut but your more aggressive less choosy eaters will likely do better in most situations, but they may also be more prone to becomeing a prey item at a smaller sizes and not be able pass their genes along. As Bill Cody would say "it depends..."
