Copper is durable, pleasing to the eye and malleable, allowing it to be shaped to fit any type of roof structure, including roof vents. On the other hand, it is one of the more expensive roof venting options and changes color over time.
Copper roofs and fittings can last a century or more. One example of durability in North America is in Quebec City, Canada. The Chateau Frontenac opened in 1893 as a posh hotel. It wasn't until 2011 that the roof over the main tower needed attention. The copper roof on the domed chapel at Annapolis Naval Academy in Maryland, built in 1902, is still going strong. Both roofs have developed the green patina of age.
That patina can be considered a pro and a con. The change in color, which can be green, blue, black or brown, is the result of a chemical reaction between the copper and the environment. The patina provides a thin, protective skin that prevents the underlying metal from corroding.
On the con side, if a homeowner expects that "new penny" look to last, it's not going to happen. It takes about six months for a roof and/or its fittings to show the color change. Choosing copper vents for a roof made of another material means the patina may clash with the rest of the roof.