If Gus knows one thing its that his offense works way better with a dual threat QB, especially one the size of Cam Newton. I think Gus gave Joey every opportunity to when the starting job this spring/fall and I think that even if Bo only slightly edged out Joey as a better passer, Joey would still start. This is the same coach that thought a backup JUCO QB could solve the offenses problem in '16. (Yes I know Lashlee was the main recruiter) and we saw how that Vanderbilt game worked out. I would still like for Gus to give him an opportunity with the full playbook though so we could just end the argument.
That being said, I have a very close relative that gets to attend a couple scrimmages/practices every Spring and Fall. When I asked who would be the starting QB he said Bo. Said the defense completely dominated the scrimmages and Bo was the only one that could actually move the ball due to being able to escape the pocket, keep his eyes down field, and make an accurate pass. He said Joey would just tuck and run every time he saw pressure and it seemed like they were trying to break him of that habit.