Well, I have come to a conclusion on my own for now.
Situation #1 winner: Brumak. Due to sheer size and strength. The Garg is tough and strong. But the Brumak is more so.
Situation #2 winner: Gargantua by a close margin. Being able to use his flamethrowers once up close gave the Gargantua this victory.
Situation #3 winner: This one goes to the Brumak. The Garg has a weakness for explosives, which the Brumak has(rocket launcher). The Brumak's machine guns don't penetrate the Garg's bullet proof armor. And the Garg's weapon's are ineffective at a range.
Keep checking in. Next match up soon. Remember to comment.