Tight connection vs taking the train

Once at the airport, stay at the airport. As you say if on time it should be more than adequate. But if you miss the connect because your flight is late, Lufthansa will still get you to Florence on time unless that is the only flight. Or take a direct to Rome and then a flight to Florence. Truthfully I would not worry about it.

I would stick with the flight and the connection through Frankfurt. I don't like Frankfurt, but I've made the connection in about the same amount of time as you have. Be prepared to move smartly upon arrival in Frankfurt. And check other departures. Luthansa has several flights a day from Frankfurt to Florence so if you miss one, there is likely to be a later flight and they will put you on it. It is easier in my opinion to trust to the connection and not have to deal with train and connection to Florence. I've done that also (fly to Rome and then train to Florence). I would rather take the Frankfurt connection by air.

Thank you both for the input. Is the signage decent in Frankfurt for flight connections and the walk and security lines doable in that 70 min span if you aren't familiar with the airport? I know it's immense & have heard the horror stories. And what about the Brussels airport? I'm in the air an hour longer between the 2 flights but have a good 2 hrs to connect. Still think Frankfurt is the way to go? And, I also, would rather not deal with 2 trains after a transatlantic flight.

It is a big airport but has the typical German efficiency. The signage is good. It is rarely for international flights to be very late so you show
D be ok.

" Would it be better to take a direct flight to Rome, catch the Leonardo express to the Rome termini, then take a train to florence? " This route is usually a little cheaper & is very easy. RMMV

The signage isn't bad at Frankfurt. I did have trouble at one point finding my next gate number, so take a few minutes to check the departures screens as soon as you find one upon exiting the plane and note the gate (and concourse letter) for your next flight. Entering and getting your passport stamped is pretty straightforward - they are used to processing a lot of people. I have been shunted to 3 different security checkpoints after passport control- they kept telling me they were closing the one I was headed to due to volume, but at least they have multiple security checkpoints and I made my connection. Make sure you follow all of the carry on rules and just be aware that everything has to go in a bin to go through the machine at security - nothing goes through loose. I have connected at Brussels also on the way home, but didn't have to go through customs or security again so I can't compare the two airports for transfers. I've done the Frankfurt transfer to Florence at least 3 times and also once to Venice in the last couple of years. I still think you will be fine and better off than with the Rome/train thing.

Thanks all. I feel better about making the connection, having heard others have done the same in a short window.