Should I have a root bone?

Hi, I'm having a debate with friend on whether our character should have a root joint or not. The root joint would be the top of the hierarchy, follow by the hips. My buddies doesn't seem to want one saying one extra joint we don't need for the engine to process. I've always had one in my previous projects which the game engine use to blend the animations from instead of from the hip.

I'm also told Unity's mecanim system doesn't deal well with an extra joint above the hip which doesn't get animated? Is that true. We plan to add IK to our character. I'm told it wants the hip joint as the root and not a root joint that is not animated.

Do you guys have a root joint in your game character or just hip?