Have only kept oscars once long ago, but there is anecdotal evidence that some color strains within a species can have different strengths, weaknesses, and behavior patterns. Electric blue jack dempsy's are known to be smaller and less aggresive than wild type fish. Any time you line breed a species to fix some triat, you take the risk of fixing deleterious traits as well (often seen in pure-breed dogs). I would have no trouble believing that albino oscars are genetically weaker than wild type fish.