As I recall, Narrative Combat involves a combination of regular combat and mass combat. The mass combat rules are used, but individual character actions influence the results. A character can enter the fray and kill enemies, they can rally their troops, they can call out the enemy captain, or a number of other actions. These actions are then integrated into the mass combat system, and players have the mass combat results described to them. You the GM only need to directly control those enemies (1d3?) very close to the PCs.
It's a combination of scales that I find appealing.
At least, that option's in Pirate Isles. I'm not sure if that's what's refered to as "Narrative Combat", and IDHMBIFOM.
If you don't have the Pirate Isles, get it. It's the best book in the series for a GM, IMHO.