I won't touch that if I were you. 1st, Arcanine isn't really a defender. A meager water Pokémon will destroy him and Vaporeons aren't really that rare. You can assume almost everyone has a decent go-to Vaporeon nowadays. Doesn't matter if you catch an enemy off guard and by surprise. It'll be demolished without much resistance. It's just gonna be a waste of stardust.
Edit:
Snarl generates more energy than Fire Fang thus allowing you to fire your charge moves more before fainting. Wild Charge is better than the rest of its charge moves when defending because of lower CD and it has higher DPS than Crunch despite Crunch being a 3 bar move.