I think this is a Rock Sissors Paper game. There will be opinions, and probally some bending of the truth.
I think it would be a smaller fish that wins. If a tiny fish were blown up in porportion to the larger fish, it's teeth get larger, skin get thicker, while the larger fish shrinks to meet the smaller contender, all the while getting thinner skin, smaller teeth, etc.
I had a 4-5" elongatus that barely weighed much and killed everything as soon as I added him to the tank ( large pleco, guppies, and barbs). But most likely unique character, seen other elongs live with cichlids peacefully.
Dunno why, I secretly want snakehead to win. Seen the aftermath of a 14" redline with a 24" jardini. 2 pieces of jardini in ziplock in the freezer.