My pressure treated deck is in need of stain and possibly a couple of
boards replaced. I'm thinking of putting on new boards instead.

The Trex looks OK, but are there other brands better? Other materials
better, such as mahogany or cedar?

The boards are 16' so no cutting, just replacing board for board. I
want to keep it simple as the frame and rails are still in perfect
shape. Joists are 16" OC.