Erza also didn't seem too different. Just Edolas Erza was on the bad guy side. But everyone was still scared as heck of her xD 

But I think, at least in the anime, that they aren't exactly opposites. Just different people with the same face and name. Possibly sharing personality traits.

I suppose it could be saying, that someone can turn out totally different depending on how they are raised.

And, also possible, be different genders from Edolas and Earthland