You make a good point crab; an uninformed decision either way will be wrong. Ditching when you have sufficient performance for a flyaway is a bad decision.
The only way to deal with this is to know: the performance in hand; the optimum rotation; and the likely drop down. It is only the marginal cases where a decision will be difficult.
Fortunately, high seas are normally associated with high winds - the aviators saviour.
Jim