Both materials can protect new and old decks from moisture damage and wear-and-tear but differ in application and cost. Deck stains cost less and don’t need a primer. The paint must have a primer applied then finished with a coat of polyurethane sealant. Deck stains don’t cover the natural grain and small cracks on the wood for a natural-looking finish. Either method works to protect your deck - choosing one over the other depends on your preference and budget.