Karachi is a living hell with people being terrorized by political parties. It's all politics that has ruined Karachi, once a peaceful and prospering city of lights. Quetta however, needs military action. The militants in Balochistan need to be taken care of, I get to see video footage and pictures daily of those men (BLA-BRA) killing innocent civilians (and military personnel) cold-blooded. When they kill the civilians, the video emerges as Pakistan Army killing innocent Balochis, but when they kill Army-men, the video emerges as freedom fighters or unknown people killing the Army-men.
Both Quetta's and Karachi's miscreants need to be engaged; however Quetta has no choice but Military operation and control (for while) while Karachi yet can be solved by Political negotiations. If the latter doesn't work, then operation is crucial. (However, don't forget here that the Political Militants are totally prepared for engaging on with Army, their arms include 14.5mm AA guns, armor-piercing bullets and over 50,000 RPG-7s. I would not be surprised to see any sort of Anti-Tank weapon.)