Re: If VI had featured Saavik instead of Valeris as the traitor
The scene in Spock's quarters basically reveals that - Valeris sees logic as the be-all and end-all, whereas Spock has the experience to understand that logic is only a part of wisdom. There's no reason to believe that all Vulcans are pacifist vegetarians like Spock is there?
Not at all. As much as Vulcans are depicted as a uniform civilization, it's important to remember that even a species that focuses so intently on logic and mental discipline is bound to have individuals who either reject or misinterpret their applications.
The irony of having a character like Valeris appear in a movie that follows Sybok's appearance can't be ignored: Sybok rejected logic in favor of emotion, whereas Valeris misunderstood the applications of logic in the real world. Whether her error is the result of inexperience, fear, or both isn't clear, but she definitely lacks the wisdom and thoughtfulness of Spock.
"He clapped his captain—his friend—on the shoulder. Yes, this man was very much like James Kirk, in all the ways that mattered." --Christopher L. Bennett-- Star Trek: Mere Anarachy, The Darkness Drops Again