Knife Min Max Crit AP Attacks SSA Dagger 30 99 90 54 3 Combat Dagger 80 140 76 56 4Because of the SSAs greater damage range and lower min, it actually falls short of the Combat Dagger 41% of the time. In other words, 41% of it's hits do less damage overall. The Combat Dagger will actually overperform the SSA's max 12.5% of the time due to it's smaller range and 2 point higher max. The SSA does 18% more critical damage in this scenario, so is that a deal breaker? Don't know.
One thing is for sure though, both knives will "miss" the same number of times. In this case, the nod has to go to the combat dagger because you can usually attack one more time with it. (If you get out to, say, 126 APs, then the difference is 2 attacks).
Of course, this all depends on if you have a choice between the two knives. Most of the time you are going to be stuck with what you've got until enough missions have been run to recover the other knife. In my recent Axis campaign, all I had to pick from initially was the SSA and the Black Jack Club, so it's a no-brainer that the SSA was chosen. On my most recent random encounter I found a Khukuri which is basically equal (or superior) to the SSA in almost every category (except for the Attack bonus). One of my scouts is now training on this weapon so only time will tell if it does the job.