We don't know anything about Jurkovec. And until he plays in some real games, we won't. If we go with his rep, he has more upside than Book. But so did Wimbush.
Book, as the incumbent with proven successful starts, should/will be the starter out of the box. That is the way it would be with most teams. But saying Book won that job by "beating out" Wimbush is disingenuous. He was the next guy on a very shallow depth chart when Wimbush couldn't master the mental aspects of running the offense much less the physical aspects of being a competent short range passer. More than anything else, that's the way Kelly rolls. His history will qbs is a clear indicator of that. He makes decisions(especially at qb) that are forced on him and Jurkovec isn't going to start, no matter what he does in practice, unless Book forces Kelly to make a change.
I just don't think Book will get much better. What you have seen is what you will see. He is a game manager, and he is good at that. He has some talents but throwing deep isn't one of them. And that is a problem in this offense.
We won't know anything until Georgia which will be a true bellwether of the rest of the season. For Jurkovec enthusiasts, the good news is that if Book is as good as his enthusiasts think he is, Jurkovec ought to get plenty of playing time in the first 2 games.