Its not possible to really compare intelligence agencies, since every intelligence agency is not made under the same conditions, or have the same objectives.
The objectives and manner of operating of intelligence agencies differ according to their nations. Some intelligence agencies have very little to do, since their country has no enemies and very little crime or corruption. Eg Scandinavian intelligence agencies. after the cold war, they have very little work. but that doesnt mean they are incapable.
Different agencies are formed for different purposes, and have different objectives. You cant compare two agencies fairly, since they may have different purposes, and also because some of their hidden agendas are not revealed to the public. Also, budget allocated to intelligence agencies are almost always higher than publicised figures, so one cant really know how efficient an intelligence agency is.
The success of an intelligence agency should be measured by the number of their objectives the agency has completed, and most of all, by how well they have kept peace in their country. also, their influence in their own nation and in enemy nations is important.
Then there's thee fact that intelligence agencies dont give info on their activities. A lot of them, like the CIA, publicise their failure and hide their successes, so as to make enemies underestimate them. The best example was when the CIA salvaged a sunken soviet golf class sub, and recieved critical info on soviet submarine tactics and codes. the project was declassified only several decades later. after all, the true strength of an intelligence agency lies in deception and secrecy. the more their enemies underestimate them, the less they will take safeguards against the agency, making it easier for the agency to carry out their operations.
In conclusion, i can say that we can only speculate whether RAW or ISI is better. Their true objectives, successes and failures will be classified for many years to come. For all we know, right now one of them might be undertaking a major operation that would destroy the other. but we wont know about it for decades. its fun to speculate, but i doubt that what we say happened or is happening is what really happened or is happening.
in my opinion, based on what i know from declassified operations, the best intelligence agency is Mossad. they have always gathered critical information about their enemies, prevented their enemies infiltrating into israeli security system successfully, prevented countless terrorist attacks, and most importantly, made sure israel always had an edge over their vastly numerically superior enemies. i doubt that israel could have won any wars without Mossad.