Attacks...

I've been debating on what's better as far as attacks when taking down a Gym. Let's say a Vaporeon has a special attack of Hydro Pump that does 90 damage and requires a full bar built up by its basic attack. Now lets say I have a Jolteon that does Thunderbolt for 55 damage but only requires half a bar built up per attack. The Jolteon can do 110 damage with two half bar special attacks to the Vaporeon's one special attack for 90 damage. Wouldn't the Jolteon be the better attacking Pokémon since he does more damage overall or is it better to use the Vaporeon since he only has to do a special attack once for 90 damage, which isn't too much less than 110 damage.

And yes I know the Vaporeon is the better Pokémon to power up overall since it can reach a much higher maximum CP compared to the Jolteon but the above example is comparing the Jolteon and Vaporeon at the same CP.