It has been stated throughout the Whonix community and other circles, especially for Torified operating systems, like Whonix, that physical isolation is the most optimal security configuration possible.
Recently Joanna (Qubes founder) wrote a white paper detailing why Qubes offers superior security than even physical isolation using traditional monolithic operating systems can.
She also details some of her own internet workflow process within Qubes to highlight its advantages.
Worth a read for those interested in the security advantages of Qubes for Whonix, as a comparison to physical isolation.
From Joanna’s blog: Physical separation vs. Software compartmentalization
Many people believe the Holy Grail of secure isolation is to use two or more physically separate machines. This belief seems so natural, that we often don't give it much thought. After all, what better isolation could we possible get than physical "airgap"?
I argue with this point of view in this new paper.