Florence VS Pisa airports

What's your final destination? If Florence, book to Florence. If somewhere along the coast, Pisa.

Pisa is a bigger airport with more airlines serving it.

If you can fly to LAX from either, I would choose the one closer to where you will be staying.

The other consideration would be the more convenient schedule.

I have no personal experience with either. Does the person who told you Pisa is better have 1st hand knowledge?

If you search back in the archives here you will find a post where our Italian transplant to San Francisco, born and raised in Florence spoke about how many flights at Florence are cancelled because of weather. Pisa much less so.

For our own trip a couple of years ago we opted to fly in and out of Pisa, but that was mainly due to the convenience of rental car pickup for a driving tour of the Tuscan countryside.
The runway at Peretola (Florence) is only 5700 ft long and I'm told that there can be seasonal cancellations (winter mostly) due to fog or adverse winds.
The runway at Pisa airport is nearly 10,000 ft long, which means that it can handle larger aircraft, plus I think the airfield doubles as a home base for an Italian Air Force squadron so the facilities are all first rate with minimal chance of a weather divert.

I have flown a couple of times from Pisa. Have stayed in Lucca the night before, it is a short and easy ride to Pisa airport. Never had a problem.

I have flown out of Florence many times, and the flights never seem to leave on time no matter how early they are scheduled. I'm always running thorough Munich or Frankfurt airports!
(I like to have my last few nights in Italy in Florence; as I save shopping till then, at the end of my trip.)

Thanks everyone for your replies. My final destination will be Los Angeles, CA.
It will be the end of trip so less cancellation challenges are best - not sure if I will be in florence or Lucca the night before I depart but if the easier, bigger airport is Pisa, that feels best
thanks again

Lucca would be a good choice for a couple of nights before a flight out of Pisa. That's how we did it ourselves and we found that the pretty little city was even more charming after the day trippers departed around 5 PM.
The train is cheap and relatively efficient for getting you to the airport, but it's a Regionale that meanders a bit and so takes a while to make the trip. It drops you at the central train station from where you can catch their People Mover tram to the airport for a nominal fee. The whole trip probably takes about an hour and 15 minutes or thereabouts.
We opted to book a private driver for the comfort and convenience involved (to minimize any potential drama on getaway day) and were quite happy with the door to door service provided - took about 30 minutes and as I recall the cost wasn't particularly outrageous.

I wouldn’t base my choice on the airport but on your overall itinerary and flight prices and convenience.
The chances of flight cancellations are slim in summer. Besides most Pisa flights are low cost while Florence has more traditional airlines

We flew out of Florence in May 2019 and swore never to do it again if we had to make a connection. We arrived at the airport hours ahead of our flight to Munich, and the airport was an utter zoo. Everyone had to get in the same line and they only had two people working at the desk. Everyone's flight was late. When we finally got on plane, we sat for another 45 minutes as they were waiting for the winds to shift. This was a sunny day in May and I hadn't noticed any wind when we were outside earlier. We missed our connection in Munich.

I haven't used the Pisa airport but my husband prefers it.