Man-Thing Very Powerful Debate, But I'm going Man-Thing on this one because He's more Intelligent in Human Form and in Man-Thing Form, And Far More Invulnerable, And his Power does more damage, Plus he can remove or cancel an ability from Swamp-Thing to Man-Thing if he really wanted too. Swamp-Thing has The Better Strength, Battle IQ, & Feats. But Man-Thing definitely has The Better IQ, Durability, Abilities, Power, Stamina/Endurance, & Hax.
Man-Thing Slays. Extreme Diff.
Man-Thing Slays. Extreme Diff.
these are the only pictures i could find but i remember seeing alot more