There is no “best gutter.” There is the best gutter for the job. As with most products, there are strong points and weak points in the various rain gutter systems. Putting up a rain gutter in an environment that it’s not well suited for, is a waste of time and money.
For most homeowners, seamless aluminum (continuous aluminum) rain gutter will give you the most bang for the buck. It’s usually available in about 20 colors from a local rain gutter contractor. Aluminum coil usually comes painted from the factory. Avoid seamless aluminum if it will be subjected to abuse (like basketballs, tricycles, etc.). Aluminum is soft and dents easily.
Also avoid using aluminum in high salt areas. If you can hear the ocean, you’re too close for aluminum. Seamless Steel rain gutter has come a long way from the old galvanized kind. Although galvanized is still available, the new seamless steel comes with an enamel coating. They will usually last a very long time but not as long as aluminum. Remember it’s still made of steel and subject to rust. Steel come in various colors but not as many as aluminum.
Also, many rain gutter contractors don’t offer Seamless Steel because the parts are harder to find. Vinyl is not suitable for the Southern California area. There is too much heat and ultraviolet rays. This causes vinyl to dry up and crack very quickly. Vinyl gutters also expand and contract to a great extent. This causes a warped and wavy look whenever the weather turns hot.
Seamless Copper is considered the top of the line. It can last for many, many years. Copper carries a certain “status”. It is, of course, more expensive. Although copper doesn’t take paint well, few people who buy copper actually want it painted. Copper will oxidize and the oxidation is turquoise. This is similar to rust on steel, except it is not caused by the metal breaking down (corrosion). The resulting “patina” or “verdigris” finish is a very sought after look. This turquoise marbling adds texture, color, and a richness to copper that is unequaled by any other metal. But like rust it can stain. If you live in an area that has a heavy marine layer, be aware that you may experience some staining from the condensation that drips off the copper gutter.