For me it's up to the players, in game and out of game. I always discuss with the players what kind of game they want, since that's reflected in how they build characters. If I have a group where the hacker is decked out with combat augments, the street samurai wants every excuse to bring his Ares Alpha into every situation, and the mage knows most combat and manipulation spells, then it's clear they want some confrontation. But even beyond that, their characters are the types to choose combat when there may be other options because they know they're prepared for it.
So my advice would be to look at your PCs and see how they've been built. Or if you don't feel you need to make it a surprise, do what I do and ask about the players' desires for the focus of the game. The best part is that combat doesn't need to go in the face of the things you like-- Intruigue and role playing. Anyone who's seen Band of Brothers or similar movies knows that war and violence can bring out the worst in people and give way to some seriously dramatic storytelling opportunities. On the other hand, you could go full-on D&D "challenge the paladin" route by having the combat they become so used to suddenly become a bit less black-and-white when they, say, are asked to remove a bunch of feral ghouls but realize they aren't quite all feral as some of them scream for the PCs to stop, which will hopefully start a bit of player debate. They have to eliminate them all or else they won't get paid and their reputation will drop. But how okay are they with killing the non-feral ghouls? Especially interesting if one escapes while they are arguing and now they have to chase it down-- Regardless of their decision to kill it or not, a wounded ghoul running through the city is going to spread HMHVV like a plague rat. How the handle the entire situation would be a great roleplaying opportunity.