Which LOR is more valued: from a professor or from my previous employer (BP) in USA for a Master's?

A Letter of Recommendation (LOR) from a professor is generally more valued for a Master's application in the USA, as it highlights your academic abilities and readiness for graduate study.

If your work experience at BP is directly relevant to your intended field, an employer's LOR can also add value by showcasing your professional skills. The strongest applications often include both types of LORs for a balanced perspective.

If you have to choose one, prioritize the professor’s LOR unless your work experience is highly relevant to your program.