On YouTube @Yuttadhammo seems to say that tranquility meditation requires focus on a concept and as a result -- i.e. because a concept is not "real" -- that meditation cannot lead to insight. And, by way of contrast, he says that the rise and fall of the abdomen can lead to insight because the abdomen (and its rise and fall) is real.
Is that -- the nature/reality of the meditation object -- the primary difference between meditation intended to achieve tranquility and that intended to achieve insight?
But if so, how does that tally with Y's answer to this question. There, he notes that the Visuddhimagga allows for insight to be achieved by scrutinising “mentality” (nāma). But how is mentality real while a concept is not?