Model animation - General

I have heard of two types of model animation. Heirchal(probably spelled wrong), and bone systems. What are the spicifics of each one?(The differences) Which one is easier to implement? And which one is faster? I want to make my own model format and need some info on how to go about it.

using keyframes is easier and faster but a lot less flexible than using bones ie the animation is restricted to how the model animator has animated it. also using bones requires less memory cause u only need to store the mesh vertice positions once whereas with keyframes with each frame the new vertice positions have to be stored

Okay, so heirchal models have to have the co-ordinates of each mesh stated for each frame. But with bones I can state it once and then simply rotate the bone to rotate the mesh correct?