Numbers don't tell the whole story, but Nichols's 2006 stats trump McNamara's in just about everything other than scoring. Nichols certainly had developed by his junior year.
http://www.orangehoops.org/2005-2006.htm
It may be the case that McNamara struggled because he was forced (I dunno if "forced" is the right word - how about "coached"?) to do things he wasn't good at (like take people off the dribble), but doesn't that support the argument that he was limited? If his team needed him to penetrate and score and he wasn't able to, that's surely not a positive thing.
It's pretty difficult to argue that McNamara was the best player on any of his teams (2006 was close, but he shot so much worse than Nichols in similar minutes); if so, "player of the decade" is a bit of a reach. His shooting numbers are just so pedestrian.