I was playing around with Blender meshes and importing them into Unity when I made an interesting discovery. In the tool shelf, under "Shading", there is a Smooth button and a Flat button. Now I already knew about these buttons. What I didn't know is that when I apply Smooth to an object and import the object into Unity, the object has less vertices than it would have had if it was set to Flat (which is the default).
I was always under the impression that applying smoothness to an object would increase the number of vertices. But it seems to be doing the opposite. This is great because I can now replace many of the objects in my game with their smoother counterparts from Blender, which should significantly reduce the number of vertices in my scene and that would be good for optimizing.