Advantages of AR are pretty simple, you don't need to spend anything on dexterity or agility to maximise effectiveness. For anyone without dexterity/agility ARs will be better in pretty much all cases. Thus an AR specialist can easily afford to get 8 strength and full perception, take full auto and use metal armour, and spend the rest on whatever they like, i.e. constitution and intelligence. SMG specialists conversely can never really have enough ability points - they need 6 agility for spec ops, 7 strength for full auto, full dexterity and full perception. They don't get enough for all of this so they need to sacrifice in one area or another and generally have nothing left over for anything else.