Just a very basic question that I’ve been wondering for some time. Is there any advantage to using one kind of empty over another?
An empty is nothing more than a location in 3D space.
The different ‘kinds’ of empties are simply different ways to display where that location is (except for the ‘image’ empty, which displays an image at the location). The only advantage to using an empty other than the default three axis cross hairs it to visualize the empty a different way in the viewport. When empties are used in rigging, you might want spheres, for example, as constraint targets. If an empty is constrained to move along one axis, you might want to remind yourself by using an arrow or a cone pointing along that axis.
Empties with images can be more convenient that background images, since they don’t disappear when you rotate the view slightly.
But, bottom line, they are different display styles for that location in 3D space, if you find it convenient to use them.
Thanks for the explanation and the examples of how the different kinds of empties can be used. That’s really helpful.