With a car Salerno is a much better choice that Sorrento. Salerno is actually on the Amalfi Coast and the most scenic area starts just a few kms from there. A good bit of the drive from Sorrento is inland until you come to the coast near Praiano. Salerno is car-friendly. Sorrento is not! It's hilly, with a one-way road system that loops around the center.
When's your trip? I've stayed in both places in February on separate trips. Sorrento's fine for Herculaneum and Pomeii by Circumvesuviana train (metro, really) but I think a car would be a liability. I stayed in Salerno with a car that I rented once I got there. I drove the AC - read about it here. In February traffic on the road was very light and I found lots of places to pull over to admire and photograph the views. Parking was cheap in the AC towns and I rarely had a problem finding a place, except in Positano.
A very good day trip from Salerno is to Paestum, stopping in the morning at Tenuto Vannulo buffalo farm with highly rated mozzarella (if you want to buy some get there very early or reserve in advance, they often sell out by noon, earlier on weekends I think). The best canolo I ever at was there and the gelato was wonderful too.
On the AC be sure to stop at Sal de Riso in Minori for to-die-for pastries. It's on the main road, a few meters from the public parking lot.
The AC is beautiful. I was
