In terms of exposure, f2.8 is a stop faster than f4. The same exposure settings are the same in any format. In terms of field of view they are approximately equivalent though the sensors have different aspect ratios. In terms of depth of field there is approximately a 2 stop difference. The 24mm f4 has shallower DOF than the 12mm f2.8. Lenses are lenses are lenses. What differs is the imaging circle and sensor size. Depends on your goal deeper or shallower depth of field can be either an advantage or a disadvantage.