Does one branch and the other doesn't? Some consider them all the same species (Euphyllia divisia = non-branching) and some refer to them as two species or sub-species (Euphyllia paradivisia = branching). It's hard to tell from the pics to me it looks like they are both branching, but the polyps look fuller on one and slightly different, I would suspect that difference was formed more from environmental conditions than by any difference in species.