Personally as a heavy I have always used the sandwich, for the primary reason that I so rarely have a medic on me at all times. And the buff they have given it is just plain epic. Forget the throw, the fact that it can restore 300 health in a few seconds is incredibly useful. Just 2 examples:
In furnace on point A I was being shot at from a distance by a spy and having rockets shot at me, normally at this point I would get off the point and try to get closer to them, but no, I just stood there, ate a sandwich, and at the end of it I had 250 health, by then the rest of my team arrived. Then at another point I was at half health, stopped, ate a sandwich, on my 2nd bite an engie ran up started hitting me with a wrench, got 3 hits on me, at this point I had about 210 health. I lowered the sandwich, pulled out my fists, then he killed me with a crit. But still, the fact that I still recovered overall, while being attacked is very impressive in my opinion anyways...