I agree with all the statements above, making allowances for terminology. The bedliner is the way to go. It won't be slippery when wet, it will last much longer, it is much more durable than powder coat, but if weight is an issue, you should be aware that bedliner is not light. You will probably be adding somewhere in the neighborhood of 40 pounds, depending on the spray thickness and amount of material being covered.
I used to work at C&S plating on Saratoga in Corpus Christi. Al researched the spray on bedliners very thoroughly before committing to one product. I was the welder in the back, so I don't know the name of the product he chose. What I do know is, whenever that stuff got sprayed on my work, it looked good, and it lasts for frickin ever! I built some pedestals for a hose trainer. She has horses with steel shoes climb and stand on these pedestals. The bedliner Al sprayed on the plywood tops is still undamaged. These things have been sitting out in the sun and taking terrible abuse for nearly ten years now.
Mill finish aluminum is cheaper than anodized or polished aluminum. The savings could be huge.
If water does get under the bedliner, salt can become trapped and cause corrosion. The risk is low, but it is there. Just pressure wash. A gentle rinse by a sprinkler won't do justice. You can also consider going to Ztech. I think they may also have a variety of colors available. I know there are other places that do. I just don't know the names of the places or the quality of their product. I can only offer testimony for Al @ C&S Plating. I know for a fact that his product is extremely high quality and he has a good eye for detail. I just don't know which eye. If you go, tell him what I have said here. That ugly old bastard will treat you right.