I'm afraid it is difficult to summarize otherwise than it was done above...
But here are my suggestions:
1. Try to avoid using either of them.
2. When accentuated (or a suffix follows it), you can't* so you'll have to decide according to the
situation (e.g. maga=to someone "lower", ön= to someone "higher" in the hierarchy),
register you wish/have to use (everyday conversation, business, media or other, official context, etc.).
3. When in doubt, use
ön if you wish to sound polite. It may be
too polite for the situation,
out of place (because of it, or otherwise) or
artificial (not natural or sincere) but at least you don't hurt the other person.
If you are not worried about it (e.g. because the difference in hierarchy is really obvious to your benefit), you can use
maga but, in any case, be ready to deal with/being able to interpret the consequences. (If you are not fluent, try it only if you feel adventurous and you think it could be useful for your learning experience. I don't think Hungarians would be hurt
really if they got
maga from you "unduly".) (Although I'm not familiar with what would happen in a drunken crowd of a rural pub.

)
* To decide about this is only partly the question of grammar (e.g. "
it is you who..."), it can be idiomatic (which may or may not coincide with your own language's rule/logic) e.g. You idiot! = Maga idióta! (Never with
ön because of the derigatory use.) You can say "Ön egy idióta!" but it is not at all idiomatic, the
ön is sarcastic (the whole sentence sounds funny because of it: you don't say
idiot to whom you'd say
ön) and it is very difficult to imagine a real situation in which you need to say this exactly.