Stainless would be more fatigue and abasion resistant then aluminum. I've used both, never had problems with either... Did have an instance of an aluminum line leaking, looked like a piece of debris off the track had bounce up and hit it or something.... Most important issue with either is good mounting of the line, keeping it away from an place where exhaust heat could become an issue. I use the hard line along the frame rails, and a piece of braided wherever flex or movment could be an issue....

I get stainless from a company called Cool Tubes, or similar--don't remember, the invoices are filed away out in the garage someplace.... The upkeep and appearance is sure easy with stainless!

I've also seen a lot of guys using the push-lok hoses instead of braided....probably a bit less money, but I just don't like rubber hoses under the car on anything....