The differences are really hard to describe, but I shall do my best.
First of all. I would suggest getting a hold of some dexedrine, it's straight d-amphetamine none of that levo shit, blah blah blah. Anyways, dexedrine has a much cleaner more lucid feel to it when compared to the geeked out over caffeinated feeling of adderall. The high is much more subtle, as in you might not really notice you're high until you've cleaned your room and organized your spice rack. Taking some dexedrine and comparing it with adderall should give you a pretty good idea what to expect though. Meth just takes it to another level. Comparing adderall to meth is a lot, there are more differences between adderall and straight d-amphetamine than d-amphetamine to meth imo
And the guy above me is mistaken (not being a dick). The synthesis of methamphetamine is different in many ways than that of regular old amphetamine, and if I'm correct is actually easier. A lot of the "it's more addictive" talk is exaggerated, but there's obviously some truth there. People can get addicted to hydrocodone after all, they'll likely graduate to heroin though if they stay on that path. I think that's a decent analogy for amphetamines too. Hell, isn't adderall fun, and doesn't it make you feel good?