I think time spent on a fight in raid has a way higher chance for stuff to go wrong vs an equivalent stretch of time in m+.
Higher penalties too.
Could say, go in blind in m+ vs raid blind for an equivalent comparison. Give both like 3 hours and see where people end up.
Probably dungeon cleared on several ++, and raid, not cleared. (If thinking heroic even.)
And likely gear rewards higher on m+ too, for the final dungeon…