No paint on decks because it will always peel. Have all the paint stripped off and then use stain for wood. It soaks into the wood rather than sitting on top. However, you cannot apply it over peeling paint because it will just continue to peel.

Agreed. You can get away with paint on al the vertical surfaces but the decking should be stripped, sanded and stained.

Arborcoat is pretty good, but you need to get all the old paint off first. Stripper applied with garden sprayer followed by power wash or an orbital sander. Expect horizontal surfaces to need maintenance every 3 years or so based on how much sun, rain and snow the deck gets. The good thing about stain though is that it will not peel in sheets like paint, so the prep isn't so bad.