In keeping with my Deadliest Warriors of Star Trek and Babylon 5 I figured I'd put Nausicaan vs. Narn as another squad on squad battle.
I imagine that what favors the Nausicaans is brute strength and a culture steeped in violence.
The Narn I imagine can be as physically strong as Nausicaans but their advantage lies in cunning and subtlety. The latter is seen in their insurgency against the Centauri. They are equally as aggressive and violent.
In short I believe the Nausicaan can outmuscle the Narn but the Narn can outsmart the Nausicaan. For squad on squad battles I would say the Narn have the advantage of tactical acumen compared to the Nausicaans.