I guess the shiny. It doesn't look too bad and I could figure out uses for Flash Fire.
It's useful in-game because many NPC trainers stupidly use Fire moves on Fire types. It's also useful competitively in double or triple battles, you can either boost up your own Pokémon or have the opponent uses a move that damage multiple Pokémon. It's also extremely useful in rotation battles because you can trick your opponent into wasting a Fire move on it.