Though I agree about Raven vs other fliers, that is for another topic. Same for Ravens being able to change height depending on target, while gunships cannot, rendering them unable to attack other aircraft from lower ground.
I mainly brought this up for balance reasons. Multiple bombs may be blocked, if the attacking bombers are far enough from each other. Of course, other units are associated, but Ravens are the most prominent example, since they always attack from a vertical direction.
Using ground-fire introduces unnecessary micromanagement, and though you might see the marks of the target's explosion through the fog of war, stopping your units from attacking ground requires additional micro again.