Why Composite? Many reasons. Composite not only looks cleaner, but it is actually easier to clean and maintain, it lasts longer, and it does not splinter! If you or your children like to go barefoot, composite is very accommodating. Composite decks keep their value now and later for much longer than pressure treated and you never have to sand and paint or stain them! It's not even a question!
Why steel frame? Steel frame is stronger, more stable, rot free, allows for more weight bearing and longer beams giving you less beams in your way, is galvanized and lasts as long as your composite deck, and is greener meaning no chemicals in the wood as well as preventing waste due to its durability.