Mulch and landscape rock are the two most common bed covers in Southwest Florida, and the right answer is often both, in different places.
Mulch
Organic mulch holds moisture, keeps roots cooler, and adds organic matter to sandy soil as it breaks down. That makes it the better choice for shrub and flower beds. It needs topping up about once a year in our heat and rain. UF/IFAS recommends about 2–3 inches, kept a few inches back from trunks and stems.
Rock
Rock lasts for years, won't float away in a summer downpour, and stays put around palms and near the house. It holds and reflects heat, so it suits tough, drought-tolerant plants better than thirsty ones. It needs a pinned weed barrier underneath, and old mulch should come out first.
A common combination
Rock in narrow strips along the foundation and around palms; mulch in planted beds; curbing between beds and lawn to keep both where they belong.