We have so many different types of project management methodologies - from waterfall, to iterative, to scrum to kanban... how to you differentiate them?

Well there are different ways to look at it. A good many of those you'll definitely find in various corners of the internet. However, there's one perspective that I do find extremely fascinating - the concept of flow. The concept derives from Physics and Mechanical Engineering, so I won't go into the details of the subject, but look more at the essence of the subject. And that is... to ask - how much of flow does one methodology bring to one project management methodology compared to another.

There are many factors to flow, but one of the key aspects is - the more number of chunks you make of something, the higher the increase in flow. A simple waterfall based project is like a big rock, when you move towards Iterative and Incremental, you start to break the rock into smaller rocks (of a few months durations each). Into Scrum, you start breaking the rocks into smaller stones (of a week to 4 week durations). And when you move into pure kanban, you start to make the stones into very small powdery dust (tasks of a few hours duration).

It does not mean one is better than the other... that depends on what you have for transportation - a crane for lifting the rock or trucks to transport the stones or water pipes to pump the sand along with water.