Smart choice. I am a proponent of BLACK colored lifetime-grade dimensional shingles so long as you have good ventilation. People think I'm crazy but they just last and are a good value. If you have algae concerns, put a strip of copper under your ridgevent, protruding out a couple inches. Rain water washing over the copper kills the algae. I would do full ice & water shield or synthetic/titanium underlayment and not 15/30 lb felt.
Our company installs just about every brand of metal panel on the market from Centria to FlexoSpan. You can get stainless standing seam panels from Flexospan and some other manufacturers but they are expensive and tough to seam. They truly last forever but it doesn't mean they won't leak if your flashings aren't done properly.
