But with Blindsight + heavy obscurement, the snakes have advantage AND a higher to-hit AND higher damage, plus disadvantage to their enemies' attacks. It's all situational, pick the animal that maches your group and/or do whatever you can with the animal your DM happens to give you.
Nice. Elk is also excellent. Less damage than the Stench Kow and slightly lower to-hit but higher mobility (therefore easier to use charge) and can knock prone to grant advantage for subsequent elk attacks (or stench kow attacks, in a mixed group).If you are looking for damage too, shoutout to the Stench Kow. Common damage resistances, same to-hit as GPS, single roll for very good damage provided you can charge and AOE poison. It doesn't have the tankiness of the GPS but 8 of these charging can unleash ----.