Ask yourself why you want composite...if it's because "you'll never have to stain it," then ask yourself why many stain companies now have products to stain composite materials...
And here's a not so great thread specifically on trex...http://www.diychatroom.com/f2/trex-d...-10043/index2/
Some of the commercial applications I've seen with composite get physical paths worn in them - like material removal. Not sure how wood would fair, but most board walks I've seen are wood and aren't worn. Not trying to be bias against them, but am also looking into this since I need to replace a deck...currently PT wood is at the top of my list