Does a grass type Pokemon do more damage with Grassy Terrain or sun boosted Growth?

Question

Will a Grass-type Pokemon when using the same grass stab move do more damage after a 50% Grass-type move boost from Grassy Terrain or from a sun boosted Growth (+2 stages in attack and sp attack)?

Answer 1

252+ SpA Life Orb Venusaur Giga Drain vs. 252 HP / 4 SpD Blastoise in Grassy Terrain: 416-494 (114.9 - 136.4%) -- guaranteed OHKO
+2 252+ SpA Life Orb Venusaur Giga Drain vs. 252 HP / 4 SpD Blastoise: 556-658 (153.5 - 181.7%) -- guaranteed OHKO

Source

As you can see from the damage calculations, Growth boosted STAB attacks will do more damage than a grass type STAB move in Grassy Terrain. Growth will take a turn to use and doesn't heal you, but it can power up all of your attacking moves.