Letter of recommendation for grad. school application source I am applying for admission to the Master's program next fall. However I am in doubt about the source of reference. I have two options:  


My mentor at a research institute who was pursuing his PhD. when I was a research intern. However, he did not complete his PhD.
Research Scientist(PhD) at my current organization where my role is that of a software developer. Therefore the recommendation is based on my work as a developer rather than on my research contributions.


Both are willing to write strong recommendations for me.

Who would be a better source of recommendation?
I would ask mentor #1 (with a master's degree) to write a letter to the PhD research scientist #2, and have the latter (#2) submit a letter for your application. Thus, the recommendation letter is received from a prestigious source, is based on current experience of your work habits and character, but can also incorporate quotes/details from the more junior person. This is not an unusual pattern in my experience.