The comments on Brewster's lack of power, especially against the run, was what I saw and heard about the player as well. But Brewster has the lateral agility and intelligence to also play Center IMO. I think his versatility and potential are what drew the Cowboys, especially after Unger was no longer available. The other Center options were not as big, or if they were big perhaps not as agile, or as experienced. Or their upside to play other line positions was limited. Of the remaining hybrid OL, only TJ Lang and Antoine Caldwell were realistic options, or good value in the 3rd. Lang, college OT, was known for being a nasty blocker, and while projected to play inside (OG) at the next level, it would still be a transition due to his lack of experience. Learning 2 new positions (OG & C) might have been problematic, especially in the short term. Caldwell is obviously the better C prospect of the three, but appears too light and not strong enough to man the OG spot in a Houck scheme, at least not for any length of time. While Caldwell had experience playing all the line spots, he did not do so with distinction. Brewster did play two OL positions with distinction (OT and OG), and if moved to center, would only be learning one new position. IMO making him less of a project and ready to contribute sooner.
A side note, I loved the Ravens pick. Webb is not just playmaker, but he is also very aggressive and physical, despite his lack of height/weight, and is versatile enough to contribute at FOUR positions (corner, safety, slot & returner). Three immediately. He would have to gain about 15 lbs of muscle to be more than a spot safety in the NFL, but he has amazing instincts and ball awareness. His 4.35 speed does not hurt one bit either. Webb was a great pick IMO.