ThanhS
Hi, Just had a question regarding choosing a recommender.
What gives more weight to your application? Does it matter more how high level the recommender is or how closely they worked with you?
Your direct supervisor (who is relatively midlevel)
Your department head
Your Global Sector Head
A client that is a large company who you have worked with?
Most schools ask that one of your LOR be from your direct supervisor, and you will usually be asked to explain why that person is not writing an LOR if they're in fact not doing so. The implication is that this person knows you best and can directly answer the school's questions regarding your abilities. In that respect, the closer you've worked with a person, even if s/he is relatively mid-level, the better the recommendation will be.
For a second LOR among your choices, I would recommend choosing the person who knows you best, and can directly speak to your specific strengths (and weaknesses). In other words, knowledge of you takes precedence over title.