immunology vs advanced physiology course for mcat

I've taken the mcat before (127 in B/B) and have an understanding of what topics are on the exam. Technically neither of these classes are needed for the exam because only a surface level understanding is required.

My main weakness on bio/biochem has been quickly understanding passages about signaling cascades and how they cause certain results in research passages.

For b/b especially I feel like performance depends on pacing than content knowledge, because I mostly miss questions that were right in the passage if read properly, but I guess more familiarity would help read passages faster? I could also practice reading scientific paper but can't get myself to do it for some reason, I feel like I need a stronger content base to do that. I also just end up improving on skills much better when required to by a class vs self study.

I have to take a class next semester, and am wondering if advanced physio or immunology would be better. They are both apparently very challenging to get an A and taught by well-regarded profs.

I plan to take the mcat some time next spring.

I taken introductory physiology and am personally more interested in advanced physio than immunology. But I assume immunology will make me learn so much about processes at the cellular level that it'll help me most in understanding the research passages I've found the hardest, even though those passages are usually not specifically about the immune system.

Has anyone here taken both classes that can vouch for one over the other?