i build decks for a living. Trex is something that you might want to think about. There is a Trex deck built by the rep located at a Payless Cashways. Here in Texas the heat and sun are unbearable. Well this deck began warping in two years. It was so bad that the rep took it off the stores display. At almost $30 for a 2 x 6 x 10, its not worth it.
The majority of my decks are PT wood. PT wood will wear and look like Redwood in six months. They all turn grey and wear the same. redwood runs about $20 for a 2 x 6 x 10. They look great at first then just turn like all of them.
PT wood is warranted for 20 years by the manufacturer and will hold up, longer if cared properly. a 2 x 6 x 10 runs about $5.