There are strains, not every "magic" mushroom is cube. (cyanes, azures, and of course animita's which aren't even psilocybin containing)
The different types of cubes however, Are really more about appearance, and location. (ie. burmese, texas, ecudor, or albino, red spore, uncut Pe.)
I belive the bruising is the oxidation of psilocybin, so shrooms that bruise really dark may have alot of psilocybin, but its being oxidized, so could very easily be degrading.
aborts are only more potent by wieght, they essentially have the same amount of psilocybin as a full grown mushroom just much less mass.