Fiberglass panels are better than plywood for storm protection because it does not rot, warp or attract termites and other wood eating bugs.
Even bees like to drill holes into wood to make nests.
Storing wood in your shed or garage that can get infested can cause other wood surrounding it to have the same problem. Over time while your plywood is stored bugs can creep from your garage and into your home.
Be sure to spray for bugs before storing wood and every 6 months after as it is like a meal waiting to happen without proper pest control.
Fiberglass on the other hand is no bugs idea of a meal and even though it may get dirty sitting in your garage or even outdoors it will always be there ready for the next hurricane.
Of course if you can find the room to store them inside all the better but they do store outdoors just as well. Some people worry that the sun beating on them will melt them but that is just not true.
We do recommend however storing them flat to prevent warping, although it is much harder to warp fiberglass by leaning it up against a wall with other stuff piled up against it.
If you do have to lean it up against a wall lay it horizontally against an even surface.
Better still don't pile things on top of your fiberglass storm panels that you will have to move should you need to pull them out in a hurry.
I can't begin to tell you how important it is to protect your windows during a hurricane but if you read the paragraphs below you may get some ideas.
Window protection is a must during severe hurricanes and is expected to be done by you according to some insurance companies.