Which one is taught better in the great state of Delaware?
Haha, just messing.... And as a show of good faith I will give you legit advice.
I dont think either one will look better. What will look better is if you get an A, so whichever one is easier to get that A (aka GPA boost). Both would be useful for med school I imagine. I have heard (depending on your school) that anatomy and phys can actually be annoying to take in undergrad because it is so babied down compared to med school - as in when you get to med school you can be frustrated by how much harder anatomy is compared to when you took it the first time. Whereas I have heard immuno can actually be decently helpful because you can in fact remember some of the contextual stuff pretty well.
But again, and I cant stress this enough, neither will inherently make you a better applicant.