We have an upper and lower deck. The upper one was built first and we used TREX brand. It is not slippery and easy to care for - just hose it down. Last fall when we had our house power washed before painting, we had the Trex power washed too and it really cleaned and brightened it up. On the lower deck, we used a similar product carried by Home Depot (don't remember if it had a special name). It was somewhat cheaper in cost, but looks great and it too is not slippery when wet. Be sure to have someone who knows what they are doing when getting this material, Trex or the Home Depot product, installed, and be sure they do not screw from the top, which leaves dimples and looks terrible. It should be screwed from the underside so that the top of the boards remain perfectly smooth with no imperfections. There are also special clips they use to space and hold the boards together - in other words it is not installed like using regular wooden boards. All this information should be available wherever you buy it - just be sure to ask for it beforehand.
Anne