I am renting a car at the Fiumicino airport in Rome and driving north to a small town call Lari just south of Pontedera and east of Livorno. Google tells me the quickest route, only by 13 minutes, is along the coast primarily on E80/ A12. The other route is to the east along E 35 and A1. Any recommendations?
The coastal route is better, there is only one short 2-lane section remaining just past the border between Lazio and Tuscany. The rest is 4-lane divided, you'll save a lot of tolls, and you'll avoid Rome's ring road.
Martelli pasta! The coastal route has considerably less traffic, doesn't pass metro areas, and costs less as it is only partially a toll road. You'll also have fewer road directions to follow. I almost always choose the coastal route between Rome and Liguria. The only drawback is there are a few areas with somewhat lower speed limits that you should watch for although there are only a couple of cameras.