Either or, but probably on Coronzon's side. What I got from the fight between Coronzon and Niang-Niang is that a nerfed mg and Coronzon are about equal when not using there big moves.
However, while Niang-Niang wasn't taking the fight seriously Coronzon was explicitly holding back to hide Hamazura's presence, and the damage she took was only cosmetic and easily healed.
So with no reason to hold back and not use her full power I'd count on Coronzon more than not, cause it doesn't seem she has the chronic problem of always playing around like the magic gods.