They are the most economical rain gutter option. Aluminum is not as strong as steel or copper, but they still hold up well to the different weather elements.
Copper Gutters
Copper gutters are low maintenance and do not rust, the major drawback with copper is that it can discolor over the years. What starts out as shiny and gold can turn to dark brown or green over time due to oxidation.
Steel Gutters
Steel gutter system holds up to the elements better than other type of gutters. They will basically last a long time. The one major drawback with steel gutter is that it can rust over time and may require you to treat them very often.