When I saw the price I was hoping to get my mast done, but the largest item they can coat at the place I went was 30', so no luck there. I am going to get my binnacle done. The hatches I had done were 2' square hatches, so opened up they were 2' x 4' each. They also had the gaskets on them still, so they had to remove those. When you think about how long surface prep for two hatches would take if I did it, the deal is especially sweet. Wish I could say the same for the risers, machine shop, and Lexan bills for my hatch project
Powdercoat is very durable, much more so than standard paint. I'm not sure how the durability compares to two-part paints, but I would think they should be similar. I made a spinnaker pole out of thin-wall aluminum tube and had it powdercoated white. The finish has held up well under the extreme beatings a spin pole is subjected to.
Powdercoating is extremely durable because is thicker and less brittle than paint, but it is also prone to corrosion behind the powder. This can easily happen on a centerboard if the centerboard is grounded. That will allow water behind the powdercoat and that can spread as corrosion which causes the whole coating to fail and flake off.
I think powdercoating is great for objects that live out of the water, but wouldn't recommend it for objects in the water.
My powdercoating experience is primarily with bicycles. I make bicycle frames and racks as a hobby and have had roughly 10 bicycles and 20 or 30 racks powdercoated.
I had an engine room vent grill done 3 years ago and it will need to be repainted soon. Granted, it's on a saltwater boat, but on the other hand, it only gets spray, it is not immersed in water.
I would probably go with hot dip galvanizing, to protect the steel, then paint only for looks, if you choose. Probably just as cheap and much better for protecting the steel.