I think Mullin could truly be a home run but I have quite a few reservations.
1) has never coached. I think he could be excellent at it potentially, but is still an unknown. Still would have to implement a style, defenses etc.
2) desire. Not everybody is a salesperson and whomever the head coach is, they have to play the roll of beckon call quite a bit with recruits etc. it's a bitter pill for some any not everybody enjoys that role.
3) should he do a poor job, how do you fire your program's golden boy? Seriously, this is a big one. Say Mullin obtains at best mediocrity. You can walk away from a guy like Lavin who did a solid if unspectacular job. It's not so easy to just punt Mullin out at head coach.
It's impossible to figure out any of those issues without hiring him first. Those are significant risks and question marks. I think maybe it's smarter to hire a guy like Hurley who is a legit choice right now, with great pedigree, great track record, was born into coaching and has few if any detractors.
I think Hurley is a clear upgrade because he has the X's and O's ability which we are certain about, great pedigree and I believe also excellent recruiter. Mullin high risk, high reward choice. Hurley low risk, high reward imo.