I try to stick with libvirt/virsh when I don't need any graphical interface (integrates beautifully with ansible [1]), or when I don't need clustering/HA (libvirt does support "clustering" at least in some capability, you can live migrate VMs between hosts, manage remote hypervisors from virsh/virt-manager, etc). On development/lab desktops I bolt virt-manager on top so I have the exact same setup as my production setup, with a nice added GUI. I heard that cockpit could be used as a web interface but have never tried it.
Proxmox on more complex setups (I try to manage it using ansible/the API as much as possible, but the web UI is a nice touch for one-shot operations).
Re incus: I don't know for sure yet. I have an old LXD setup at work that I'd like to migrate to something else, but I figured that since both libvirt and proxmox support management of LXC containers, I might as well consolidate and use one of these instead.