I've lurked for awhile but this is my first post.
So right now I can get one strong LOR from a (I think) well-known professor I am doing research with and another one from a non-prof with a physics PhD who has publications that I am also doing research with and who always praises me for my work. The problem is the 3rd LOR and I have two options.
Professor A: Did about 6 months of theory research in the Fall in String Theory. I had to basically read chapters from a textbook and then present the material to him one-on-one. It was a great learning experience and he already agreed to write a LOR for me. My concerns are that I'm not sure how the LOR would turn out (not that I have reason to believe he would write negatively about me) and he is a professor overseas (Japan) so I don't know how committees view that.
Professor B: Got an A in his modern physics course and seemed to make a strong impression with him. He has previously written two LOR's for me for other things and I know from an adviser that one of them he wrote was very strong and helped get me into my exchange program. My concerns are that I am going into my 4th year and that class with him was in the Fall of my sophomore year.
Thanks for any help or advice.