The champion in CoC1 is the stronger of the two. and it's really not even remotely close. beating the wraith just isn't an impressive feat when it already has a gaping chest wound and a goddess is still doing most of the heavy lifting. I'd be willing to grant that Kas and Lethice are about even but the champ in CoC1 fought her and her entire horde alone, CoC2 champ needs companions every step of the way.And this may be a bit wanky but I'd say killing a Wraith that was equal to a weakened Lumia (even if it was with help) is far more impressive to anything CoC1 Champ has done. This can just be base Champ too without any soulbinds.
Also want to throw out that soulbinds don't make the character any stronger just unlocks new abilities that are on par with every other ability in the game.