Out of the two I would go with the first one since Venusaur has mostly Special Attack moves but a couple of Attack moves like Razor Leaf. But if you plan on EV training them you should get better natures.
if i find a mild nature with hp20 att10 def9 spatt12 spdef12 spd10 (this is the best so far i could find) it only makes 1 point spatck diffrence with lvl 50 pokemon ,4point diffrence with lvl 100 pokemon.