There are unique pros and cons to both asphalt shingles and metal roofing, so your decision boils down to what drawbacks you’re happiest to live with. Metal roofs are quick to install, they keep rain out for many decades, and the material can be recycled when the roof is no good. On the downside, metal can lead to large and sudden snow slides off the roof, and the surface can be noisy in heavy rains. And though a metal roof can keep out water for 50 years or more, I have yet to see the painted factory finish on metal roofing look good after 25 years.
Asphalt shingles generally cost less than metal, and their rough surface prevents snow slides. The best asphalt shingles sport a 50 year warranty, and some even carry a lifetime warranty. Asphalt roofs look classier than metal, in my opinion, and it’s easier to make valleys reliably water tight. That being said, asphalt shingles aren’t as green a building material as roofing metal because shingles can’t yet be economically recycled and they are made with petroleum-based ingredients. For what it’s worth, I’ve chosen asphalt shingles for my own buildings and projects, but there are lots of people out there who swear by metal.