Huh. Good point. I never really thought of it that way. I would be a bit more convinced that this is true if either of them were one gender, but that doesn't mean it's not a good theory.

I think they might represent male and female beauty. Ninetales is said to be a very beautiful creature, and that, basically, disrespecting it's beauty can curse you. Kind of like in PMD: Red and Blue, where Gengar was a cursed human who had touched a Nintales' tail.

Arcanine is also very big and strong, very masculine. I'm sure even it has some sort of legends based on it, that are some sort of "Respect Me Or Parish" warning.