Advice on choosing recommenders Currently applying for master programs in US and UK, in the track of media and communications / marketing. I don’t have many connections with Professors and here and my options:

The project coordinator, who is a graduate student in my lab. The lab is huge with 50+ people so I didn’t interact with the PI. But I have worked with this coordinator for 4 semesters.
The PI of the lab mentioned above - I also took her seminar class and was doing well, participating a lot. I’m thinking to have both 1 and 2 write my letters, the former detailing work ethic and latter detailing academic performance.
A part-time lecturer, who’s not a PhD, that taught a summer design class. Her class was very hands-on, project-based, and I really loved her class and went to a lot of office hours. A lot of group work and communication skills were involved in the class. I’m just not sure how her titles might impact the letter.
A professor who taught an exam-based class, no projects whatsoever. I sat in her front rows for the entire semester but didn’t go to her office hour or interact with her. I got an A+ in the class.

Basically I need three letters and was thinking to ask #1,#2,#3 but some people suggested that #3 might not be a good option. I’m wondering if I should go with #4 instead.
In your specific case, I would rank them 1, 3, 2, 4, with 4 not actually being a real option if you can avoid it.
My reasoning is that a truly good letter from an individual familiar with your work will always outweigh a mediocre letter from someone who doesn't.  Given that, it then becomes more important who exactly is writing the letter.  A letter from a famous faculty member with decades of experience and awards that just says &quot;this person came to class and did their homework&quot; is not going to help you stand out, even assuming that person would agree to write such a letter.
Number 4 doesn't know your work, and probably doesn't really know you either.  It doesn't matter how influential they might be; they simply can't write a letter recommending you in anything more than generic terms.
Number 2 sounds like it could be the most important writer, and while the degree of exposure you've had to them helps, the lack of a close working relationship probably hurts a bit, which is why I would rank them after number 1.
Number 3 lacks the prestige, if you will, of the others, but as one who worked closely with you and saw your work ethic up close, they should be able to write a very good, very specific, letter.