Cedar decking and railing defiantly looks nicer than treated lumber. It can be sanded to remove a stain or a burn on the surface, or to achieve a smooth surface without worry of removing the chemical added to the treated lumber. Cedar can be easily cleaned with a deck cleaner and the increase in cost is only about 12% over treated decking on the entire project. The under structure would still be treated lumber and the labour would be the same with either wood.
It's hard to find cons for this product, as it is such a beautiful wood with natural preservatives to fight decay and insects. But, the lumber is not the same as it used to be when cedar was harvested from the old growth redwoods. Todays cedar is harvested from sustainable younger growth trees with less of natures preservatives.
Do not expect cedar to last longer than treated lumber.
If I could, I would install cedar decking all the time. I love being able to select the best looking lumber for the railings and be able to sand the surface to furniture quality. It is a huge step up from treated lumber in the way it looks, without the huge expense