I own 4 trailers, 2 galvanized, one steel, and one aluminum that I use for my snowmobiles. The aluminum one cost $ 1000 (vs. $ 650 if I had bought a similar galvanized one). While towing around on salted New England roads A LOT of gunk coats our trailer and even finds its way inside the frames. I am sick of worrying what the corrosion inside of the frame looks like while going 65 mph with 1500 lbs behind me. Now, I only use the steel trailer for "around town" trips. The galvanized ones I climb all over before each trip searching for trouble (but you can't see inside!). The aluminum trailer I only look at the welds. For me, the peace of mind is worth the extra. I know also, up here at least, the resale on an aluminum trailer is almost the same as a new trailer regardless of age. Definately not so with Galvanized or Steel.

On a side note: Has anyone ever seen a trailer treated with that spray-on bedliner stuff? I wonder how that would be for corrosion protection.