I am applying for CS PhD programs in the US, most of which require 3 recommendation letters. I have already gotten two letters from my previous university advisors (a professor and an assistant professor), and I believe they will be strong letters. But there is still one left, for which I have two choices:
My manager from a previous employer.
- He knew me well and also promoted me once. So I could expect a strong letter from him.
- However, he has little contact with academia and doesn't have a PhD degree. Plus, he is not that much older than me. So, I even doubt whether he knows how to write letters for academia or not.
The boss of my manager, a chief scientist.
- He is a very famous scholar in the field of my study. I guess it's good to have a letter with big name.
- However, he didn't know me well. We've spoken a few times but that is. There is a possibility that he refuses to write for me, and even if he does, the letter will be mild at best.
Moreover, I think it's unwise for me to try both because I need the reference of my manager if I want the chief scientist to write for me. But if he refuses, then it would turn my manager to look like a compromise choice, which could be awkward for him.
I am looking for advice on this choice. Much appreciation for your opinion!