The fixed miter saw is a far safer machine than the sliding miter saw. To avoid having the saw run forward during a cut, you should push the saw back to make the cut. The problem is that this can lift the work piece and jam the blade. Once again, clamps or hold-downs are critical aids to properly using a sliding miter saw.
Then there is the technique of the double cut - either for getting both sides of plastic laminates to cut clean - or for a perfectly square cut in very hard massive wood.