Personally, I would think a helmet from the guy who designed the originals, new mold or not, would probably be good.
As for the Efx helmet, I have a friend Whit who bought one and walked around at C6 in it and said his looked better than some of the 501st sculpts he saw.
Still, JKNO owns a few. I would pm him and get his take. He sure hasn't steered me wrong.