Hello,
Here are my thoughts:
1) A structured interview is a typical interview that you must have ideally prepared for: a detailed prompt, exhibits with charts and graphs, very clear and detailed information available throughout the case
2) A structured interview thus tests among other things a) data interpretation skills b) analytical skills
3) An unstructured interview is one where the prompt is vague and open ended. It requires the candidate to thing big picture and requires a lot of creativity and brainstorming in addition to other skills. There are rarely any exhibits, and the interview heavily relies on the candidates to drive the case forward.
4) An unstructured interview is very popular in the middle east to simulate real life cases that are also very big picture and greenfield.
I specialize in giving mocks for unstructured cases based on the real interviews I have received from interviews. Happy to give you mocks if you're interested.
Feel free to reach out to me via chat!
All the best!
Rushabh