I've found that the "best" polish for the job is very dependent on how bad the part you are cleaning is to start with. For example, if you already have a nice shiny part, the Mother's "Billet" polish will make it shinier... shinier than the regular mag wheel and aluminum polish... BUT... if you have a not-so-nice part, the standard mag wheel polish will shine it up better than the "Billet" polish will, because it has more abrasives and cleaners in it. Its basically a process of steps... using the harshest stuff first, such as steel wool or fine sandpaper, then working down to the "best" polish, or should i say, the least abrasive polish, to achieve the best end result.
With that said, i had a set of aluminum aftermarket wheels on my truck that sat outside not driven all winter, and the wheels were a mess... fine pits, and discoloration,etc. back when they were clean, the Mothers "billet" polish worked to make them shine the best, but it did very little to improve the look of them when they were really crappy looking. I took some 00 steel wool to each wheel, til all the marks and pits were gone, then used the standard Mothers mag polish on them, THEN finished off with the Billet polish, and then (and only then) did the billet polish really make a difference.
Also... i recently sampled some of the Meguiar's alumunium polish in their "NXT" synthetic line and found it to be some super good stuff... its in a blue can with a neon green lid if i'm not mistaken... I'm planning to pick some up myself in the near future. Based onthe sample i had, i think its even better than the Mother's billet polish, and is cheaper too.