Upcut bits are the go to choice where having a clean bottom surface or getting maximum chip evacuation is most important. The up cut action of the bit pulls the chips up and out of the cut allowing for maximum chip evacuation. Because the chips are being pulled up this will result in a clean bottom edge of the cut

The multi-rabbet bit steps in 1/16" increments from a 1/8" cut width to 1/2", simply by switching ball-bearing guides.