2. . . .In Mirror Episodes you know what races are ahead and who is reluctant to serve. . .
As a footnote, even though "Mirror, Mirror" was filmed when racial tension in the United States was at its heigth, there is no racism shown in the episode.
Yeah, I never noticed any racism either. Though it was cool that the Vulcans seemed to have a mafia aura about them.
The mirror universe concept was something that simply couldn't hold up under scrutiny. Which is why I think only Mirror, Mirror