I think it's personal preference. I like the smaller feel of FLL and been enough times to know my way around. I do wish there was a better transport from T3 and T4 to the car rentals than the terminal bus and I wish the terminals had good sit down areas to eat but I find it easier to navigate, easier to get to the car rentals and now that you don't have to go north to the u turn to be able to head south it's a bit quicker to leave. There's a hotel in FLL we really like and our first stop is Ihop then Walgreens across the street so you may as well say it's habit for us.
I did rent a car to go from FLL to MIA since we were staying at Comfort Suites but we had some shopping to do. I returned the car and and all I could think was this place is pure chaos. I was with my son. We topped the car with gas and brought it back and we took the shuttle back to the hotel. It would have been quicker to walk back and if I didn't have my son I would have done that. Now I have not flown in r out of MIA this is just the surroundings, my preference is FLL. And last year we flew into FLL and drove to Orlando. I won't be doing that again. 3 hour drive wasn't worth it for me.