Which letter of reference would be better: from a teacher who knows me well or from one in the same institution I am applying for who doesn't know me? I am applying for a second masters degree at the same institution I am currently at.
I have requested my current course teacher to write me an LoR (letter of reference). However, I am facing the problem that he may not know me that well. I didn't have many interactions with him during the online lectures or seminars this year because of the covid situation. The only way he learnt about me was through a mock exam which I got a score slightly above distinction (I am in the UK). So I think he may only be able to write a very general letter.
I also asked teachers from my bachelor's degree. I built a very strong relationship with them and did extremely well in their courses. So I am pretty sure that their letters will be filled with details.
I previously thought that my current teacher would not be willing to provide me with a letter because he didn't get back to me for more than two weeks. But now I am in a dilemma. On one hand, his endorsement would be more reliable and powerful in the sense that he is in the same institution. On the other, his letter will be quite general. So should I still ask him?
Thanks in advance for any solid advice!
Generally speaking, the LOR that recites a lot of detail and describes a long relationship is more helpful.  When I write an LOR, I assume the reader has no idea who I am or what my standards are.  So, that's why I try to give a lot of objective information about my relationship with the student, so the reader can decide for themselves whether they agree the evidence supports my recommendation.  I'm sometimes asked for LORs from students I don't know very well.  Perhaps they're sophomore and they were in my section of a large intro CS class.  I try my best but realistically those LORs will never be as helpful as the ones I write about a student I've known for several years, was in a small class where I really got to know their work, has been in my office a lot, worked for me as instructional aide for a class I taught, etc.