See, I have to book a round trip, and can't do 'sf->venice' as one leg and 'florence->sf' as the other.
Florence is, oddly, cheaper than Milan.
It is a conundrum. I think I'm going to do Florence, because it's not a long train jaunt to Venice, and I am leaving from Florence.
Though I think I may try for an 8 hour layover in Paris, on the way home.
I still need to see the bijouterie that Mucha designed.