Pizza isn't really/doesn't have to be that unhealthy. Fast food takeaway pizza is of course, but 'pizza' is redundant in that.
Pretty much all that makes a homemade or otherwise decent pizza less healthy than a sandwich is the amount of it one typically eats in a sitting. Or of course if you for some reason pile unhealthy stuff high on your pizzas, but stuff your sandwiches with the height of nutrition. But I assume that would be uncommon.