It's all those attributes. The larger head means longer mains. Inherit power can also come from thicker beams, stiffness, balance, swing weight, static weight, etc. Either a combination of certain aspects or all of them combined.
For my money, nothing beats a healthy static weight. Even if the swing weight is low, the beam is thin, the head is smaller and the flex, low; if the static weight is up there, likely chances are I'll be happy.