Decent leisure fares used to require the purchase of a roundtrip with a Saturday night stay. But that's seldom the case these days for domestic flights to Florida.
Leisure travelers can often get more convenient flight times and lower fares by purchasing two one-way tickets, often using two different airlines -- instead of buying a roundtrip itinerary on a single airline.
The only problem is that there are then two change fees (when using the cheapest fares on AA, Delta, United, or US Airways) if it's necessary to change travel dates. Usually this mean the tickets are worthless because each change fee exceeds the value of each ticket.
Some passengers are concerned about the TSA with two one-way tickets.
The 9/11 terrorists had purchased first-class, one-way tickets, so passengers with one-way tickets were more likely to be flagged for additional screening soon after the attack. Your boarding pass could be flagged with the letters SSSS, triggering additional screening. Or the airline gate agent might not accept your bags until they were hand-inspected.
That was a long time ago.
Although there are still people who think that one-way tickets increase the chance of being selected for an additional security screening or baggage inspection, that seems unlikely to me. Presumably the TSA watches for suspicious activity, but I can't see how one-way tickets constitute any sort of additional risk. In fact, someone with evil intent would be more likely to buy a roundtrip, given even the slight possibility that a one-ticket would trigger more scrutiny from the TSA.