Most people are choosing vinyl siding over aluminum because most grades of vinyl siding cost less. Aluminum is still more common for commercial uses, however, because of other advantages.
Aluminum siding holds up better in extreme temperatures. Vinyl becomes brittle in very cold weather, which can cause cracking and splitting. It also can melt if it encounters extreme heat, such as a barbecue grill placed too close to the building, and sometimes even a clothes dryer vent can cause problems.
Aluminum siding is more flexible and can be bent easily, so it is commonly used for trim with vinyl siding.
Because vinyl expands and contracts with temperature changes, it cannot be sealed at windows and doors or in the trim areas. Wind-driven water can be blown into the tiny gaps. Waterproofing is commonly installed at these areas, but it also may be punctured by siding nails.
With vinyl, color is added during manufacturing, so it penetrates the entire structure. Aluminum only has a thin layer of enamel coating, so scratching reveals the metal color underneath.
Aluminum siding develops a chalky buildup over time because of weather and erosion of the enamel, leaving it with a faded appearance. Vinyl also fades with time. Both can be painted.