Yes, the MTT might be good for Quintana, though it also suits Costa, since it´s not too steep and it´s steady. Weight advantage for Costa, engine advantage for Costa.
In all, I see Costa ahead. He now has quite some experience how to ride these 7-10 day stage races successfully.
In all, I think it´s great that South Americans are on the rise, but they´ve still to prove that there´s a new era comparewable to the days of Herrera et al. But they´re all pretty young, so time is on their side. They just have to avoid the approach Rujano has chosen, whatever approach this was and still is - Rujano has been a mystery ever since his 2005 Giro.