Regarding the Peter Preston stuff, and why I think the theatrical cut is better for TWOK, the theatrical cut plays as if Scott and everybody are concerned for the loss of life generally. With no personal connection established, Preston plays as a representative of all the cadets killed. If he is singled out for any particular reason among the casualties, it is only because he stayed at his post and died while other trainees abandoned their posts.
I find it a sad commentary on the franchise to insist that there must be a personal connection for the main characters to care about the loss of subordinates. Fans have accused Kirk of not caring about the loss of redshirts on landing parties, although I've generally found such criticisms to be unwarranted, as in fact Kirk was generally shown on TOS to care. It's therefore somewhat ironic if on the other hand a Trek film will get criticized for showing Kirk and crew caring for the death of a random cadet serving aboard ship.