https://www.smartertravel.com/allegiant-retires-outdated-aircraft-safety-concerns/
Please look at UPDATED safety-they have since retired the planes that were cause for concern. Things DO change.
The pros of Sanford is it is a much smaller airport, so tend to have less flights if something does happen to delay. Security is a breeze, and renting a car is super easy. The drive isn't bad at all but we've had a removable transponder for sunpass for a couple years, so the toll drive is fast and easy.
The cons-like any budget airline check all the fees-heck with Allegiant they charge for online CC use-it is cheaper to go to airport to buy tickets with cash! Budget airlines also tend to have much less flights so again-if delay or cancel that flight you may be stuck for a couple days. It is also a bit longer to Orlando, no magical express etc. When whole family goes we tend to rent a car anyway-our oldest, and myself and DH have all lived in and are comfortable driving in large crazy traffic cities, but not everyone is (totally understandable!!)
We've flown Allegiant a few times as they are the only direct flight from our hometown. We've also driven to larger airport (3 hours) for more flights on other airlines (and after major weather related delays coming home from Miami after a cruise, then driving home meant we were up for almost 24 hours straight). In our delayed case-I think I would have rather stayed an extra day in Miami, and arrive at our home town vs the nightmare of hanging in airports for hours, but I realize that is not an option for many.