Well, this might be quite late. From my playthrough, I notice a few things. Besides from Ves and Roche feeling on the witcher's decision, there is also another consequence from the action which no one had mentioned before (from my search on the same topic). Not sure if I am wrong in my observation. If the witcher spare the Nilfgardian officer, the village of Mulbrydale do not suffer from any destruction. However, if the witcher decided to end the officer's life, the village will be razed. A few houses will be burned down and the armorer will be lost forever. You wont find the armorer in the village.