Combined arms all the way. My reasoning is that bludgeoning weapons like hammers are good at breaking bones and enemy knockdowns, and that slashing weapons are great for body part severs and quickly ending fights. Slashers are able to do this more quickly once the enemy is down on the ground and less able to dodge, which means buddying up with hammers is a great tactic.
Generally I try to shoot for 8 man squads split between hammers and either axes or swords. Sometimes I mix up the hammers with some maces, if a migrant comes that has skill with that weapon. Even if some of them are sleeping or whatever when the hour comes, a given station order should still yield two or more of each damage type. This also means I can be assured of multiple damage types at the point of attack even if I don't have multiple squads on the scene, which is beneficial during ambushes where attacks can materialize from multiple directions. The swords squad tends to see more frontline action against siegers and opponents with squishy insides (since they get a piercing attack as well)- the axes are first to fight undead and inorganics. I also try to have at least one squad of pure crossbows, more if I can keep them equipped. They're like the cavalry the game doesn't have yet- expensive to maintain, a significant time investment to train, but extremely effective on the battlefield.
You can influence who the first responders in a given squad are by assigning weapons based on agility- high agility hammers will show up on the scene first, and often will break legs and chip bones, slowing the enemy down enough for the rest of the squad to arrive. If you're facing organized resistance, try to order them to a staging point first so they don't get too separated.