Depends on what you are looking for. The beaches on the Gulf of Mexico (West coast of Florida) tend to be prettier with whiter and wider sand, clearer and warmer water, but little to no wave action. Depending on what you are looking for and how far you want to go, there are also some great locations for shelling. The Gulf beaches are further from WDW.
The beaches on the Atlantic Ocean (East coast) tend to not be as pretty, but the water is a bit cooler and murky. You can get some decent wave action most days ( not giant waves, just decent). The closest Atlantic beaches are closer to Disney than the closest Gulf beaches. There are also still a few Atlantic beaches you can drive a car on if that is appealing to you.