Stripper, although, it's very caustic to work with.
Now, as far as the discussion about using SS brushes.....I've been an AWS certified welder since 4/17/99, and I second the statement about only using a SS brush to clean aluminum, as well as cleaning SS. Steel brushes leave iron residue. In welding, this is an impurity that will compromise the integrity of a weld.
But if you doubt what I am telling you, then pull out an AWS procedure handbook, and read about GTAW and GMAW aluminum welding, and proper cleaning procedures. They tell you to use SS, not regular steel brushes for cleaning, again, because steel contaminates aluminum.
Using a steel brush for cleaning, this leaves all kinds of little particles of iron embedded into the aluminum, as soon as it's exposed to moisture, it will likely leave little specks all over the aluminum, unless it is thoroughly washed with an etching acid such as phosphoric acid, and then rinsing with water.
As far as the SS wire wheel, the knotted type IS a bit more aggressive than the plain type, you have to go easy with it and use light pressure, or it will gouge the metal.
BTW, 6 dollars for a SS wheel is one helluva deal, considering that I paid about 50 dollars for one I bought from McMaster-Carr a couple of years ago. But then again, mine is stamped "316" meaning it is genuine stainless with no impurities.
Can't say for sure about the HF wheel, I haven't tried one, but at that price, I intend to give it a shot.