Book can still throw deep, he just throws it more accurately
he throws it more accurately, period or he throws the deep ball more accurately?
It's too bad there isnt any real good articles out there analytically comparing these two. I.E. breaking down just deep throws, or just RPO's, etc.
just some personal opinion pieces like this:
https://www.onefootdown.com/2018/9/20/17884838/notre-dame-football-stop-calling-for-brandon-wimbush-to-be-benched-fighting-irish
Wimbush for his career is 181-356 (50.8%) for 2,476 yards 17 TD's and 10 Int
Book is 49-78 (62.8%) for 469 yards 5 TD's and 4 int (think what his stat line would be like if he didnt have the couple gimme TD's thrown this year, yuck)
If we extrapolate for direct comparison: 224-356 2,141 Yards 23 TD's and 18 Int
If you did the blind test on that I'm not sure QB #2 would win in a land slide. sure completion percentage is big change but QB#1 has more yards, and almost half the turnovers.
The one thing I do agree in the article above on is neither of these guys are likely taking the Irish to the promise land. Wimbush has too many throwing issues and Book isnt dynamic enough.
ND isn't some Bama like juggernaut that can afford to have below extraordinary QB play. Hell even very good Clemson teams with Watson couldn't beat Bama in some years.
Wimbush is closest thing we have to a QB who is that dynamic, he just isn't proficient enough throwing the football.
But 12-3 as a starter is damn good and hard to complain about, imo.