2014 Florida Code: Section 1506.5 NAILS - The corrosion resistance shall meet ASTM A 641, Class 1 or an equal corrosion resistance by coating, electro galvanization, mechanical galvanization, hot dipped galvanization, stainless steel, nonferrous metal and alloys or other suitable corrosion-resistant material.
Stainless Steel - Made of type 316 stainless chromium-nickel steel with molybdenum which icreases corrosion-resistance, improves pitting resistance and increases strength at high temperatures.
These fasteners provide the maximum in corrosion protection. These would be ideal in your part of the country considering the salty conditions. Very defined ribbing in the shank which provides maximum protection in high wind conditions. Cost averages at about $11.00 per pound.
Hot Dipped Galvanized - These are steel nails immersed in melted zinc. The zinc coating is much thicker than standard electro plated steel nails. The steel is manufactured with a ribbed shank, but the hot dipping fills in the grooves which reduced the strength of the ribs. Cost averages at about $5.00 per pound.
Electro Galvanized - These are zinc plated steel nails. The zinc is not nearly as thick as hot dipped galvanizing. These nails are often not even recommended for outdoor usage. They usually have a smooth shank which will result in a lot of nail pops. Cost averages at about $2.25 per pound.
Is it worth it to pay more? The better the fastener, the more likely they are not to fail in extreme weather conditions. All of these nails meet the required criteria. I would suggest either stainless steel or hot dipped galvanized. The electro galvanized are okay for felting and roll roofing but not really a good choice for shingles.
Note: Costs are based on current metal prices and will change over time. You can always expect stainless steel to be the most expensive. The hot dipped will be usually at about half of the stainless cost and the electro galvanized is usually a little less than half that of the hot dipped. You get what you pay for when it comes to nails of all types.