Movepool:
Arcanaine: Thunder Fang, Flame Wheel/Flare Drive, Crunch, Aerial Ace, Return/Extreme Speed, Iron Tail
Rapidash: Poison Stab, Megahorn, Flame Wheel/Flare Drive, Quick Attack/Return, Bounce, Iron Tail,
Flareon: Fire Fang, Iron Tail, Return/Quick Attack,
Aracanine wins with movepool. He has the same amount as Rapidash, but his moves are a little more productive. He can cover his Water weakness. Second is Rapidash because she does have more variety than poor Flareon who stumbles across the finish line.
Stats:
Arcanine: HP: 90/ Atk: 110/ Def: 80/ Sp. Atk: 100/ Sp. Def: 80/ Spd: 95
Rapidash: HP: 65/ Atk: 100/ Def: 70/ Sp. Atk: 80/ Sp. Def: 80/ Spd: 105
Flareon: HP:65/ Atk:130/Def: 60/ Sp. Atk: 95/ Sp. Def: 110/ Spd: 65
HP: Arcanine
Attack: Flareon
Defense: Arcanine
Sp. Attack: Arcanine
Sp. Def: Flareon
Speed: Rapidash
Arcanine beats 'em in stats and in movepool. Battlewise, he is the better choice, but by personal preference, and I love Arcanine, I would pick Rapidash.