The Martial Arts (Quality) is best thought of as completely disassociated from Martial Arts (the Unarmed Combat Specialiation). It's a whole different ball of wax, seperate entirely from the skill.
Martial Arts (Qualities) give you bonuses to certain things (like extra damage value for certain attacks), or give you extra goodies that modify or alter an existing rule (like letting you partially ignore the modifier for Firing in a Melee, letting you Ready Weapon more quickly, or letting you deal damage with a Disarm).
Martial Arts (the Unarmed Combat Specialization) is among the vaguest Specializations in the game, but like all other Specializations all it does is give you +2 dice to apropriate skill rolls. It has nothing at all to do with the Quality, or Maneuvers, or anything else listed under the Martial Arts rules in Arsenal.
What aspects of Krav Maga or Firefight are you interested in, specifically? The more specific the question, the more specific the answer can be.