Wow dude.
Chi-Chi is tough as fucking fuck. She was trained by her father, King Ox. She birthed two Saiyans, so she clearly has ovaries of solid brass. Goku, the OP god-stomping mary sue meathead fucktard that he is, is utterly terrified of his wife, causing some of his opponents to worry Chi Chi is actually stronger than him.
Valka Haddock herself is merely a fairly strong viking woman. We don't see her in direct combat very much, so we can only assume she is baseline nordic female - which based on other feats by other women in the Berk tribe, is pretty god damned badass. What Valka has going for her is she wields dragon. Pure, fucking dragon. She understands them, can tame them, can live among them. Like Yoda, size doesn't matter. Valka can wield all dragons the same. She can ride them. She can direct them. She can dance with them. If you fuck with Valka, you don't just fuck with a baseline nordic woman, you fuck with ALL GOD FUCKING DRAGONS.
I'm going to go with Valka. Here me out.
Chi Chi has the edge in one-on-one, no ally fisticuffs. Even if they were the same species of human, Chi Chi has more one-on-one combat experience. Seeing she's in danger, Valka's dragon pals jump in and being dragonstomping Chi Chi. Fighting dragons takes some fucking training that Chi Chi doesn't have, so now the advantage is on Valka's side.
"But wait!" you're going to say, "If we're calling allies into the fight, Chi Chi's huband and two sons are OP Mary-Sue god stomping meathead fucktards who can blow up planets and shit!"
Well you're technically correct. Either Carrot, Rice or Understanding the Heavens could single handedly obliterate every dragon in the HTTYD canon. Unfortunately, Gohan and Goten are off studying and avoiding violence like good little mother-fearing children, and Goku has too much respect for the sanctity of a fight to interfere, even if his friends and family are dying1.
1 imagine this links to the scene in DBZA where they say "You talk like death doesn't matter" - "IT LITERALLY DOESN'T." I don't remember where that scene happened.