If I'm not mistaken, I think Acid/Solar Beam is actually Victreebel's highest DPS moveset. It's not rated "best" because the two moves are different types (poison & grass) and Pokémon that are weak to one type probably won't be to the other. But even with a poison-type quick move, this Victreebel should still be lethal to water-types.
Should I power up this Victreebel? 100% IV
Answers
Acid gives 10 energy per use while Razor Leaf gives 12.
If you're dodging then you're not looking at EPS or DPS since you're not going to be attacking off every cooldown, you're going to be attacking once in between each dodge, where you'd rather have the higher damage as well as the higher energy for a single attack.
The lower cooldown does not make a difference against most water pokemon who use Water Gun, which is what you're probably going to be using Victreebel against.
Between each Water Gun you can only use one attack, so the lower cooldown doesn't make a difference.
Anyway the super effective damage from Razor Leaf more than makes up for the extra DPS that comes from being able to use charge moves sooner due to higher EPS.
If you're spamming the moves off cooldown, in the time it takes for you to use Razor Leaf to 100 energy, then Solar Beam, you'd have done Acid + Solar Beam and an extra Acid. That one extra attack does not do more damage than the extra damage that comes from using Razor Leaf over Acid.
I would think about to power one Victreebell only with tons of dust (like 350000+) and many top tier pokemon maxed out. Imagine if you catch/hatch/evolve a top tier with high IV and nice moveset (Lapras, Dragonite, Arcanine, Snorlax, Vaporeon, Exeggutor etc), with only 4k dust and spending in a Victreebell. Reserve him and farm dust like a hell.
I would not power that up or a Vilplume neither. Acid and Razor leaf are both horrible quick moves. I dont think its possible to do two attacks and dodge with either of those moves.
If your looking for Vapreaon counters go with a Parasect with bugbite solar untill you have a proper Venusaur. Bugbite is an unbelievably powerful quick move, one of the best in the game.