I'd hate to hear years later that Ireland overruled Philbin and didn't choose the QB he wanted.
Anyone that can't see the benefit of signing Flynn and giving him a HC and OC he's worked with his entire Pro career doesn't want the new regime to win their way.
Not too mention if you sign Peyton, you have to commit another high draft pick to QB in the next year or so.
If you sign Flynn, you can draft a low round prospect to develop and use your high round pick for other areas of need.
After factoring in draft strategy, health, money and the impact it has on the coach's system, I see ZERO upside to signing Peyton.
And if you don't get to the SuperBowl after signing Peyton, everything was a bust. If you sign Peyton, your prime directive is to get to the SuperBowl IMMEDIATELY. Nothing else will suffice.
Flynn is the obvious choice.