The moving head has most of the body of the
fixture mounted on a moving
yoke. The moving mirror swivels and twists the mirror to that position given the light
fixture itself is housed within a non-moving body. This is much easier to do.
This allows for more gadgets in a body that does not require engineering to allow for this inside of the moving body. On the other
hand it results in a little less ability to move in a half circle plus. On the other
hand, since it's only a mirror moving, it can often move it faster at a cheaper cost.
For the momey, most of the moving mirror fixtures will be good to start with. As long as you can heft the
fixture into place - in the case of some older styles, you get just about what you do with a moving head
fixture. They can also be useful for low ceiling height areas.
Is it the best solution, probably not but given a limited playing area such as a
stage, such fixtures can often provide sufficient lighting.