What you need realy depends on where you are going to be.
If sticking to inshore around the bays on the coast, then a handheld will be fine. Given our flat terrain, the constant traffic on the ICW and other boat traffic, odds are someone is going to be in range. Plus you get the weather.
If venturing offshore or into more remote areas, or if its on a larger boat like a center console, get a standard unit with a full antenna. Like noted above, VHF is line of site. Even with a 6' antenna, on a small boat (16-20' CC) you will probably only get 12 miles range at full power. The big Charter boats and tugs get longer range because their antenna are mounted very high and they use huge whips.
Some will disagree with this, but given cell phone coverage and technology today, if the areas you hunt are all in cell coverage (mine area), IMO you are almost better off with a cell phone than a handheld VHF these days. A small cell phone in a waterproof ziplock is a lot easier to keep on you at all times vs a bulky waterproof handheld. And if you have a blackberry/smart phone, you have instant access to weather radar, real time observations/bouy reports, etc.. And,if you are on inland waters like some of our big lakes (Seminole for example), very few, if anyone will be monitoring VHF.