Before you even think of driving anywhere in Italy, make sure you know about the somewhat unusual driving rules here - look at the FAQs on the subject on the upper right hand side of this page.
The Via Finiguerra is much the most convenient for anybody in the historic center - but I've been driving in Florence for almost 50 years.
If I were you, I wouldn't dream of using either office you mention. I would pay the extra money to go to the airport and pick up the car there. The airport is a two minute drive from the Autostrada A-1, which will take you south towards Perugia.
If you use either Via Finiguerra or Via del Sansovino, it will be a bit of a struggle to get to the autostrada, and there is always a chance you will violate the dreaded ZTL rules.