Short answer: Agility. that's what boosts your stabby weapons, which give you your +12 stabby 3 bonus. Better answer: It depends. If you have access to all the best equipment possible for your level, you would have an awesome stabby weapon and power cards on your gear that buffed some agility, but mostly dodge and damage. Since you probably don't, you may have access to a strength-based weapon that deals more damage than any stabby weapon you can buy in the bazaar or pass through your shared bank, even considering talent bonuses. If that's the case, be sure you've trained the appropriate weapon talents as far as you can and get strength boosting gear over agility boosting gear in the bazaar.