STAIN, STAIN, STAIN.
Once you paint you are married to it. The stain, especially one of the newer decking stains, will allow the wood to breath better and trap less moisture. The stain will wear off like paint, but will never peel off like paint. The stains are easier to apply, dry more quickly, recoat easier and will last. If your wood is very dry/brittle you can add boiled linseed oil (up to 1 gallon per 5 gallons of stain) to increase water beading and rejuvinate the wood surface. Clean and prepare properly using one of the deck washes. Two thin coats beat one heavy coat. Can be easily re-stained the following year with a quick rinse and another coat of stain.
Eric
