Everyone that has done any sort of athletics in their life, knows what a pull up is and for good reason. The pull up is one of the best strength exercise for anything involving pulling, including rowing, swimming, muscle ups, and even the Olympic lifts. I am a believer that strict pull ups need to be the foundation for strength building in that area, however the kip and butterfly have their place when it comes to speed workouts, or high volume. That being said, anyone wanting to get a stronger pull needs to focus on strict pull ups. Here is a great video about pull ups and technique with the butterfly and kip.
Exercise: 75 strict pull ups for time