As much as I love Devin, and as good as Devin used to lock Parker down in our series in 2006, I had to go with Parker. He was more efficient in FG% and assist to turnover ratio.
Gonna have to go with Parker. He is (somewhat) more of a prototypical PG, whereas Devin Harris is like Gilbert Arenas, a SG in a PG's body. Parker takes better care of the ball, which puts him over the hump for me.