When applying to graduate programs in computer science, what are the pros/cons of having the professor who advised your project in an NSF REU in computer science write one of the required letters of recommendation? I ask since the duration of REU programs are so short (~10 weeks).
More specifically, assuming a good letter can be written by all professors, why might I have my 3 letters consist of:
Case A: 2 CS professors from undergrad, 1 CS professor from REU
Case B: 1 CS professor from undergrad, 1 math professor from undergrad, 1 CS professor from REU
Case C: 2 CS professors from undergrad, 1 math professor from undergrad