That's a nice overview. Looks like Whonix with physical isolation and Qubes OS with physical isolation are about even. You might still prefer Qubes OS so you can create disposable VMs to open untrusted files, or store your passwords in text files that are in a separate encrypted VM from your browser. I guess Whonix with virtual isolation is less secure that Qubes OS because VirtualBox is less secure than Xen. Are kernel exploits to gain root privileges more of a threat than VirtualBox exploits to escape the VM?