there are many different abrasive levels in metal polishes and certain brands do seem to offer a difference. Some of my favs include Mothers Billet or PowerAluminum, English Custom Polishes, and Wolfgang Metalwerks.
I've found that I do not really like to polish metal with something that's too abrasive if im going to do metal I find myself using PP becasue its as abrasive as i want it and i don't have to worry about marring the metal.....its a chemical polish which means very very fine polishers are in it and the product does most of the work instead of them. Just my $.02
I use Menzerena metal polish (looks like a small tube of toothpaste). It's not cheap but it is amazing. I've polished the metal on shotguns worth $10K+