I have heard the aluminum doesn't survive a second loading, the steel can be reloaded if it is boxer-primed, which much of it actually is, but you don't want to load it hot and you only get two or three loadings out of it, compared to the several times most brass will hold up to. It isn't dangerous to reload it, it will simply fail (crack at the neck), the same way regular brass does, much sooner.
As far as brass, you will basically have to try what you have and see. A-Merc is definitely crap by all accounts that I have ever come across, and just about every other brand has had their bad batches here and there, so you can't really say that all of X is good or bad. Everything from brass that won't resize all the way ( I don't mean all the way down either), to primer pockets that are loose after the first shot. All you can do is try it out and see how it goes.
