/etc/network/interfaces - difference between auto and allow-hotplug

I am running Debian 9.13. I tried to check what is the difference between auto eth1 and allow-hotplug eth1 in /etc/network/interfaces. I have eth1 networking interface connected via USB. I tried rebooting, running systemctl restart networking and plugging/unplugging and it seems that main difference between allow-hotplug and auto is that if interface is marked as auto, command systemctl restart networking fails when eth1 is not connected. This leads to the conclusion that allow-hotplug is in fact preferable in all cases maybe except situation where I know that interface won't go away (lo, built-in interfaces). Is it correct? Is there any other difference?