Every car I've ever driven in allows you to have it on the front and floor vents at the same time, not sure what your driving or where...I live somewhere much colder and seemingly have more experience warming a vehicle. Spend any extended time with heat coming out the vents and your feet will be frozen and your face will be dry.
Heat to the floor or 50/50 floor and defrost are superior options (even if you aren't using a vent mounted phone).