I don't pretend to be a huge draftnik, but it seems like consensus is that Warren is an elite prospect at his position whereas McMillan is much more flawed but the position happens to be more valuable. Warren seems like a guy with more realistic chance to be making pro bowls and all pro teams.
In general though, I think Gronk, Kelce, Kittle dominating the league at the same time kind of inflated how fans think of TEs and their ability to be "#1 receiver" types. The absolute very best like this guys... sure. But even the second and third tier TEs, while they might be "elite" at their position" don't really dictate coverage and terrorize coordinators the way fans think. At any given time there are "X" number of truly special talents at the TE spot but once you get past that couple of guys you have ones who might still make pro bowls and all pro teams but aren't really THAT impactful IMO. They can be a key cog in the offense but usually they just aren't explosive enough to really dictate coverage.