I prefer longer TATL flights as those offer more time to sleep, so ATL over a JFK or BOS. (I believe FCO is the longest doubt you euros from Atlanta) I also prefer the TATL to put me in my destination city, but that's not always an option. If you're going to need to connect, AMS/CDG/FCO/LHR/ETC (I've seen DUS and MAD before) are all basically the same. The next question would be if you want to fly AF/KL/VS to Europe instead of Delta. Assuming price is the same, and the over all trip length the same, I'd fly Delta to CDG and then on to Florence.