RAW is a spy agency from what is known publicly. ISI is the wing of Pakistani army which is into sabotage and terrorism in neighboring countries. ISI has the best and brightest of Pakistani army and they run ISI- well trained in warfare. RAW is a more cerebral force which can detect enemy actions and build strategy which may or may not get implemented. Most RAW chiefs have been gentlemen who have been IPS officers - and hence are not into waging war which ISI indulges in.