I use a shaving razor only as I am afraid to use use a shaving machine because it might cause cuts in the skin. But I remember my father using a machine. I am yet to try.
Machines ar not as much efficient as razors. When you use a machine remeins shadovs on your face, it is true that with razors you may cut your self but when you user a good razor and you are carefully it dosen`t happen.