EBJD in general are weaker, less aggressive and more prone to diseases at a young age than the regular JDs, in fact many people here have chosen not to keep em anymore because they can't deal with raising a fish for months and having it die suddenly for no reason. Yes, there's a lot of success stories, you might get one and raise it successfully without even noticing a difference, but many other people have had bad experiences with them... "prone to diseases" doesn't mean all of them get sick or die, it just means you're at a greater risk of encountering some kind of problem when keeping these instead of the regular fish.
If they were perfectly normal and competitive they would be found in the wild living alongside common JDs, but they're not.