Butterflies aren't good for much more than cutting yourself or intimidating someone else.  You need to decide how much you want to spend.  What you pay for is what you're going to get.  If you want a knife that will last a lifetime and actually hold an edge, you're looking at more than $100.  Benchmade is probably what you're looking for, they're not the best, but they're pretty good.  Gerber makes very good cheaper knives, but don't expect it to cut well.  Basically any stainless steel is going to be shit.  I'd say that for what you want, go benchmade.