[Mike Swearingen]

Properly treated pressure-treated wood manufactured by a reputable company (Weyerhaeuser, G-P, etc.) comes with a 50-year limited warranty, and cedar doesn't AND will not last as long.
Decking choice is one thing, foundation structure is another. Your call.
Make certain that your contractor is using p-t wood that has the proper treatment level for in-ground use, if you go that way.
Mike

 

[Mike Swearingen]

If it were me, I would use p-t posts anchored to the concrete with cedar boards nailed onto them similar to a boxed beam.
We have p-t 4X4 posts anchored on our porches with Atlantic white cedar nailed over them. Look great!
Mike