I am way out of my element, but feeling the need to show some ignorance.
Aluminum is lighter and I can see why there are some passionate responses here. But aluminum has its weaknesses which can to some extent depend on its series, how it is treated, when it is treated and when the shaping occurs. 6061can be as prone to cracking as 5000 series. There are some applications where a series is better for certain tasks, but in the end, aluminum likes to fail earlier in the fatigue cycle than let's say steel. The huge advantage is weight, but at 600 bucks, my guess is the manufacturers are obtaining a series and then shaping. The metal is already heat treated before the process not during to obtain a desired characteristic.. I might be wrong tho..