Hi
texaslong22,
Thank you for your post. You seem to have a few compelling options, which is a good problem to have!
My first reaction is that you do not have anyone from your current job. Can you not ask someone from the tech firm? Can't let them know you're applying? That's okay, and it happens, but it will be worth explaining why via a few sentences, either in the application field where they ask you ("If you did not provide a recommendation from your current supervisor, please explain why..."), or within the Optional Essay / Additional Information.
Beyond that, the honest and nuanced answer is that it's a little tough to say in a vacuum -- without knowing what the rest of your profile is, strengths and weaknesses are (and therefore how each recommender can potentially gap-fill), and what each recommender would specifically be able to address from a strengths, projects, and even constructive feedback example. That said, my lean based on the information you've provided is toward the Principal. Even though the other two have MBAs from HBS, the Principal appears to have had the deepest and most significant management of / engagement with you. Just make sure that if he hasn't done this before, he knows what a modern-day MBA recommendation needs to look like from an insightfulness and specificity standpoint, and make sure that he is not going to overlap too much with the Partner's recommendation. (They can be complementary but shouldn't be redundant.)
If you have any questions, would like to provide more information (so we can hash this out "in actual context"), and/or wish to further this conversation, please feel free to sign up for a Free Consultation. I would be happy to share additional thoughts!
https://www.avantiprep.com/free-consultation.htmlBest Regards,
Greg