Ok, so I've got a few professors I can ask for a recommendation letter. I'm just not sure who to ask.
Professor 1: Will have 2 summers and 2 semesters of research experience with him. He's in the field I'm applying to for grad school, though he's a professor for a different engineering major. I'm definitely going to ask him.
Professor 2: Will have 2 semesters of project experience with him. The project, although not real research, has many similarities to research. For example, we had weekly update reports, had to work in teams, we were basically on our own since the professor didn't know anything about the coding API (it was a coding project). I think besides coming up with data, it was almost an actual research experience. The professor is a distinguished professor, though he's in a different field. Nonetheless, he should be a safe bet for a LoR. He might not be able to talk about any actual research, but I'm sure he'll be able to say some good things about my research potential.
Here's where it gets tricky: I'm not sure whom to ask for the 3rd letter
Professor 3: He co-supervised the coding project with Professor 2. He's a distinguished professor as well, once again, not in my field. I'm not sure if I should ask him since he'll probably say the exact same things as professor 2 (seeing how they co-supervised the same project)
Professor 4: Took a class with him. Had some interesting conversations. I'm possibly taking another class/independent study with him. He's somewhat in my field (my field is pretty interdisciplinary).
Professor 5: Took a class with him. TA'ed a class under him for 3 semesters. I came up with the idea of having undergraduate TA evaluations for the class.
Professor 6: Did a research project under him for a semester. Didn't get to see him much, mainly interacted with a graduate student. The experience was interesting. I thought the graduate mentor was being unrealistic with his expectations. Needless to say, I thought I was seriously disappointing him. Apparently he told the professor I'm very motivated and dedicated. Nonetheless, I rather not ask, I still feel the graduate student would mention several negative things about me.
Any advice would be seriously appreciated. I always wondered, what do adcoms think about letters from 2 professors who basically say the same thing (since they co-supervised)? Would it be better to go with Professor 4 instead of Professor 3?