Yeah this question is relatively subjective.
Some find memorization easy, in which case they find subjects like Micro, Biochem easy. Others might find the conceptual stuff easy (although I haven't met many of those folks), making physio easier.
But since Step 1 is all about integrating subjects together, there is no such thing as an easy subject and equal importance should be given to all the subjects you've listed. Lesser importance can be given to subjects like genetics, cell bio etc (coz they'll always have ridiculously tough or experimental q's in those categories.)