The advantages are:
1. Hummers are accustomed to foraging at different levels so it's more natural for them.
2. One ant guard protects both feeders.
3. Less blowing, therefore spillage, in high winds, at least for the top feeder.
4. Have more feeding ports in their favored locations.
It's ridiculously easy to make. Just hang a wire from a feeder, then use an "S" shaped wire to hang between the two feeders, or you can buy those S hooks. I made mine from a small section of a wire coat hanger.
Below is a young male Rufous. I saw at least 3 today here in Alpine.