Which is better, a water bottle made out of steel or one made out of aluminum?
Water is heavy, why add more weight to it by using a steel bottle. You might also take along one of the filtration kits so you can refill the one bottle you are carrying.
Aluminim is the way to go. I have an aluminum water bottle and so far it has been great. The bottle doesn't give the water any bad added flavor and it is lighter. Downside is that my water bottle has several dents in it but they just add character.
Unless okorder / A lightweight Nalgene BPA free water bottle
Aluminum IF you get one that is anodized on the inside (like the Sigg models). Otherwise it will corrode if you fill it with acidic liquids like fruit juice (which will also leach the aluminum out of the walls and there are some who believe ingesting aluminum isn't good for your health in the long run.) There are also lightweight stainless steel bottles that are pretty good, but somewhat heavier.