>>48090576It has a *unique* secondary typing, not a good one
They both have four weaknesses (and share three of them), but Venusaur doesn't have a x4 weakness to Ice and it's not weak to Bug (it's weak to psychic, which is much easier to deal with). Torterra takes shitloads from U-Turn and has much lower special bulk, making it take those ice and fire attacks worse.
Torterra has one immunity (to electric), but only two resistances (ground and rock).
Venusaur doesn't have a type immunity, but he is immune to being poisoned, and he has FIVE resistances (electric, grass, fairy, fighting, water). Against three of those he has a type advantage, against one of them he has numerous SE coverage moves to take care of them, and while he lacks SE coverage over fighting enemy fighting types just can't do much against him unless they're Hawlucha or Zapdos-G.
Meanwhile, Torterra can't check water types because he's only neutral to them, and will get blasted away by their ice coverage. Any electric type will either switch out or worse, U-Turn out for good damage. His two resistances just don't make up for his weaknesses.
That's also not getting into how Mega-Venusaur removes two of his weaknesses, making him neutral to fire and ice, giving him an extremely good defensive typing that's only two weaknesses are easy to check (just grab Tyranitar).
