Should I retake a course for an easy A or focus on research? I’m an incoming PhD student deciding on courses to take. A normal course load is 3. There aren’t many being offered this semester, the only third option is a course I took as a MS student last semester at another school (we have no transfer credit policy). I could take the course for a slightly easier A, since my program has high grade standards and my peers seem highly capable. My study adviser suggested this as it would free up time next year to prepare for the qualifying exam. However, I want to continue an old research project from my MS in addition to starting a new research project. During COVID times, I figure a light courseload is best, and any extra time translates to research progress. Next semester I can take 4 courses to make up for it.
After deciding on just 2 courses this semester, my friends and study adviser still suggested I retake the 3rd course. The lectures are just 2.5 hrs a week, but even if they are easy homework/projects might add up and research is my top priority. As for the course material, I loved the course last semester, but with less novel material it might be less interesting.
Should I follow my friends and adviser’s guidance, or should I focus on research now until I finish my old project and have a lighter first PhD/COVID semester?
PhD students are judged on their research publications, not their coursework.  It is good strategy to minimize the time you spend on courses.

we have no transfer credit policy

If there is no policy, ask for one.
I would recommend taking a low effort course over a high effort course; not to reduce effort expended, but to direct that effort to research.  If a course helps you with your research, then take it.
I would not recommend lowering your coursework efforts to the point that you fail; in that case you will need to repeat the effort, which is not efficient.