I don't know much about heat pumps--just a little. Pool heating is an ideal application--the outside air is warm (in heat pump terms--in the 50's or higher) so they get into their super-efficient range, far more so than gas.

H/Ps have a bad rep because they were used for heating and cooling houses in Northern Virginia (near DC) where it's far too cold for them to be efficient in the winter. But for pools they are supposed to be terrific.

They are expensive to install--2 to 3x what a gas heater costs, but far more efficient. If you need to heat a pool fast, though, they aren't so good--gas is better. But keeping it warm? I gather they can't be beat.

Are they better than solar? In some ways yes, in some ways no.

If you can do both, it would be great. You are in Florida, though, where you get lots and lots of sun.