At HB Fence, Decking & Construction, we use galvanized screws on every wooden project. If your fence will be planked with an untreated wood such as cedar or redwood; the zinc coating on the galvanized screws helps prevent your fence from rusting and staining or discoloring fence planks.
Galvanized screws will look much better in the end especially if left with a natural, unfinished look. The screws resist loosening up during wind storms. Nails will get looser as time goes on and can deteriorate and bleed on the wood.