I'm VP of our family treated lumber wholesale business, so I may be able to help a little on material selection.
Of the composites listed in this thread, Timbertech is the one I would choose over the others. We prefer not to sell Trex or similar products as we see TT hold it's color and shape for a longer time than others.
That being said, I always suggest using 2x material on a deck surface to customers. The #2 stuff you see at any home improvement or lumberyard is going to be wet and will not last as long as advertised. It's young growth and not very dense. Besides, the #2 of today is junk compared to the same from 20+ years ago.
I prefer to sell #1 KDAT from Culpeper Wood Preservers or a KDAT #2 Prime. Most east coast yards can order from Culpeper through Weyerhauser Distribution. If the your yard has a good relationship with it's treater, you can ask them to have the wet #2 kiln dried after treatment for an additonal special order cost.
I don't like 5/4 as it will twist and check as it dries. Plus the added thickness of 2x material will last longer IMO.
Beat up Ranger on stickies