Aluminum arrows are (in general) more consistent in spine, weight tolerance, and straightness than even high end hunting carbon arrows. Some aluminum arrows will bend easily if they are mistreated (shot at non-arrow targets, such as metal and rock), normally the thin walled ones are prone to bending if mistreated. Aluminum arrows also offer a much larger number of options as to what arrow you want to shoot, as they are made in MANY more spine sizes. Many aluminums are made of various diameters and wall thicknesses with the same spine, allowing choices between light and fast, or slower but more durable. Top quality aluminum arrows (such as Easton XX78s) are relatively cheap, around $70 a dozen for shafts.
Carbon arrows are more durable (depending on the shot). They are also much more expensive.