re: Metal roof question

If you install the metal roof with exposed fasteners you should have a layer of "ice and water shield" membrane under it. This will seal around the screws and keep the total package dryer for a longer time frame. This type of roof panel is also thinner, probably 26 or 28 gauge material without a Kynar paint finish, which fades faster.
A standing seam roof is a true architectural grade product if you get it in 24gauge galvanized steel or .032 aluminum, with the kynar paint finish, which has a 20 year fade guarantee. The concealed fasteners help insure a watertight system. However you should still use thee ice and water membrane in all valleys. This will be four to five times more costly than architectural shingles and should last your lifetime.
Large hail will dent any metal roof.