Militarily speaking, it would seem more sensible to stun than kill. Killed soldiers are not cared for (except perhaps hours, days or weeks after the battle, by some overburdened field chaplain and his two shovel-toting assistants), since they aren't worth anything. But stunned ones are valuable combat resources once they wake up, so their fellows would be interested in dragging them to safety, or otherwise securing them against further threats. Thus, killing one guy stops one guy (and perhaps at best makes the others hesitate a bit) but stunning one guy stops three guys at least. That was one of the considerations when NATO went for 5.56 mm bullets rather than the more powerful 7.62 mm standard of their opponents: wounding is more effective than killing.
We've never really seen people recover from stun blasts in a matter of mere minutes, unless the stun was deliberately administered to be of little effect (say, "Samaritan Snare" where the Pakleds toy with LaForge). Stunned people tend to remain stunned. And our heroes seem to trust their lives on this, too, never bothering to secure a stunned victim with, say, futuristic cable binders or duct tape.
There thus shouldn't be any technological or tactical reason to use kill over stun in that fight, not unless the STXI timeline Starfleet had somehow failed to develop sufficiently good stun guns where the TOS timeline Starfleet had demonstrably succeeded. The reasons would be purely psychological. I guess ShatKirk would never shoot to kill; he went for the soft approach even in ST3, with the Klingon sons who had just murdered his bastard, and it took a Special Dramatic Moment to turn ShatKirk into a killer and not rescue Kruge from falling into the lava pit. But PineKirk could simply be different.
The more interesting question is, would QuintoSpock be more intent on killing than NimoySpock? The poor guy did just witness death of his planet and mother and so forth - but NimoySpock had seemed psychologically incapable of feelings of vengeance, and QuintoSpock was supposed to be the same as NimoySpock at least right until meeting Cadet PineKirk. Would QuintoSpock suddenly start killing out of spite?
(Just out of curiosity, how do we know our heroes shot to kill in the movie? Were the beams of different color or what? The one time I saw the movie, I was way too intoxicated to remember much detail.)
Timo Saloniemi
