Treated lumber. Yeah, it’ll rot in 20ish years give or take, but it’s half the cost or less for the materials and probably so much easier to work with it’ll reduce labor costs (whether you’re diy’ing or paying someone). If you maintain it by sealing or painting every year or two you can easily get longer lifetimes. This composite, you scratch it, there’s no fixing it. You cut a bird wrong, there’s no cheating it.