metalheadz would win due to the armour covering the cranium and protecting the temple which will minimize the risk of a one punch knockout.
however if a hospital lands on u, u are fucked no matter how much armour u have on.
metalheadz will use its speed and good defensive abilty.
hospital will use its liquid power and heal itself every now n then.
metalheadz have darker tunes though so they will use witchcraft to demolish the hospital
it would be a good fight though i wouldnt mind watching it