Very small airports have advantages regarding parking, check-in/baggage claim and where applicable, customs since there are fewer people using the airport. The bad news is there are probably fewer airlines who fly out of that airport meaning fewer choice of flight times and/or connections vs non-stop. Make sure you see where the connections go. If you go from Sanford to Orlando (for example) and then onto other destinations, not sure there is any advantage. Very small airports tend to connect through other nearby cities/hubs and tend to have few/if any non-stop flights.
If there is any kind of weather or mechanical delay, could be several days before the next plane is available.
I would imagine the price of renting a car would be cheaper then taking any kind of online taxi or car service. Generally, those are mostly intended for short trips.