Is it a covered porch, or a narrow-covered balcony like at a condo? If the furniture is protected, you can get good deals on the teak at Laplace in Destin, much cheaper than Smith & Hawkin. Ours has lasted five years.
On uncovered porches or on narrow balconies that are covered, it depends on your budget. I like the resin stuff because it is durable and is renter-proof. But everything resin I've seen is pricey. If you don't have a big budget, I'd try Home Depot. Don't get wood if the furniture is unprotected from the elements. From our experience it lasts six months to a year and then it rots, regardless of how much money you pay for it.