IMHO defensive prowess at premium positions generally benefits your pitchers to a more significant degree than offensive prowess. So C, CF, SS, 2B are positions that I would be OK with one or two players who profile +10 D/-10 O. I think the corners, (LF, RF, 3B and 1B) are where you can have one or two +10 O/-10 D types. 3B tends to be a corner spot where a stellar defender can change the course of a game or series, however.
I also believe that defensive skill is more highly correlated with superb athleticism; whereas offensive skills are less highly correlated with athleticism. In other words, it's rare to see a great defender who is not a great athlete; but there are many excellent hitters who are not very athletic.
I think the O's like players who can defend at a very high level. I think they like exceptional athletes who are versatile defensively. They have been fortunate that many of their prospects are superb on both sides of the ball.