it boils down to what a player is trying to accomplish on tour. if the answer is to win as many of the biggest tournaments as possible, win the most money, and hold a position at the top of the sport for as long as possible, then you have your answer.
if your objective is to eventually identify some as-yet-to-be-named arch nemesis and achieve a winning record against that player, then maybe you've got a case for nadal. but if we took a poll among past and present tour members as to which goal they'd prefer to accomplish during their career, i know where i'd put my money.
honestly this is an absurd argument. having to scurry off into the marginalia to unearth tortured shreds of logic to defend a position that's refuted by every commonly accepted metric of success should tell you you're on the losing side of history. i'd prefer my legacy not be written in the liner notes, but that's just me.