Base power and energy charge mean nothing if you don't take into account the duration of the moves. You want to look at Damage per Turn and Energy gain per Turn, or per duration. The choice then depends on your available charge moves and how the different moveset combinations perform in the key matchups you expect to play. Many pokemon only have one viable fast move because there's so much difference in performance.
In your example, VW has 2,5 DPT and 4 EPT, while RL has 5,5 DPT and 2 EPT. For Venusaur and Meganium with FP, both are good options. For nearly any other grass mon I'd recommend RL because that DPT is insane.