From a roleplaying standpoint, convincing a guard to let you pass is more fitting for a good char while the double reward (charisma XP + kill) doesn't make too much sense. But on the other hand you don't want to give the players the same reward (XP + gear) for a game of R-P-S (charisma can be maxed out without even investing a single point) as fighting a dozend guys that are above your own level. Also what if you choose the peaceful solution, but still want to pickpocket them/ see what is in the chest in their base and get cought?
On the surface, that game of RPS might seem easier, but consider this: You MUST be able to win in combat. There are almost guaranteed to be tougher battles than the one that you are skipping through dialog, usually before that point. This means that you have already proven that your character is strong enough to win through a fight.
By being able to win through dialog, you prove that your character can not only fight, but also talk. The sum total of the minimum stats you need to win both combat and dialog are higher than the minimum to win in combat. Therefor, from a strategic stat-allocation perspective, dialogs are actually harder than combat.
I'm talking in a general sense, not in regards to DivOS specifically. I should note though that in DivOS charisma can't be maxed out "for free". It's effective past 5, you can only get 3 points on gear (one of which being a unique late-game piece), and the talent has an attribute penalty. Even just putting forth the strategic effort to acquire and put on the gear is additional effort beyond combat. Also, because DivOS's charisma dialogs can come unexpectedly in combat zones savescumming (cheating) would be necessary to properly use the gear, and should combat start anyway your character will be equipped wrong, therefor creating an additional risk.
