Introspection vs. Observation is a good way of looking at it I'd say., but I think they're all used in correlation.
Sensory types tend to primarily observe what is going on around them in a sensory way, noticing how people and things look, sound, smell etc. Keen observers are those naturally attuned to details, and memory of details. Keen observers make great investigators, never missing a detail. They can tell when someone looks different than before, down to minutia. Observation is of what's tangible. For example: construction workers working with physical objects will use observational skills much more than reflective skills. They keep track of different tools, measurements, etc., and reference them by name. Interior decorators keep track of color names on paint swatches, styles of furniture and other things, and are good at tangibly organizing a space to meet both emotional needs and a specific set of data that the clients ask for.
From what I understand, Introspection and Intuition are slightly different at times, but work together as one most of the time. Introspection, I'd say, is used in different ways. NF's use introspection in a, identity based way, reflecting on how they themselves and other people feel (Like a counsellor or teacher, who use introspection to understand the way in which to interact with and understand other people and their needs). NT's reflect on how things work, how to make things work, and what they can improve upon. (Like an engineer or architect, who use introspection to come up with new innovative ideas to make things work better and advance technology, architecture, manufacturing etc.)
Intuition, I'd say, is the place that these new ideas come from. Introspection is just the process in which the mind processes and understands the intuitive thoughts. It's like the information that supports the intuition is woven together in a framework. When this framework is viewed as a whole, the intuitive answer is realized. The intuitive answer is always there, but through introspection, you see the pieces of the framework that make the intuitive answer make sense. With introverted intuition in particular, I think that as we gather information, it gets stored away in multiple different frameworks (or webs of infrormation) that the brain categorizes subconsciously and automatically. When the framework has been fully developed, the intuitive idea has been formed. Then, through introspection, these frameworks are reviewed, recognized, and then consciously understood in pieces, until "aha!" an idea emerges.
I think that with observation, information is taken in aswell, but instead of mostly being stored away in frameworks, it's stored away in memory. It's like this information is stacked and organized like an archive. Then, when confronted with a situation where a decision needs to be made, relevant information is pulled from the stacks, and the decision can now be made. Keen observers are also good at comparing and contrasting things, and recognizing how things look, feel, taste, smell... Because of their good memories, they can recall two or more tangible things or people that are similar on a factual basis, "this looks like that", "that sounds like this". Because they can recognize and understand their five senses, they tend to experience the present moment with more vivid detail, even without consciously thinking about it.
