I grew up in a family that owned a lumber supply company so take this with a retailer's grain of salt.
Cedar is beautiful, so is Mahogony, but be prepared to pay dearly for it and have to maintain it every year.
Trex (just the brand I have the most experience with) may not be the most attractive option but as stated before you will never have to do anything but power wash it, it will outlast the pressure treated lumber you use to support it and you will never have to dig a piece of it out of your foot. It was originally deisgned for use on piers and ocean bordwalks. A lot of the mildew problems are caused by incorrect installation or areas that don't get any sun (which would make wooden decks have similar problems).
Save the cedar for railings and ballusters if you want that look but I would not put any natural wood down as the actual part I am going to walk on.
I see decking like I see roof shingles. People pay dearly for fancy architectural shingles and the last time they actually notice them is the first day the roof is finished. Decking is something you are going to walk on, it's not crown molding.
Just my
