I think in the end it is about what you are interested in/what YOU individually are good at.
EX: I'm a chemistry major, and I absolutely LOVE O-Chem, I do undergrad research in it, and I don't find it difficult, I find it interesting. Same for gen-chem.
However, any biology study that is unrelated to humans drives me crazy. I hated learning about insects, birds, plants, etc. I subsequently (sp) spent much less time studying this information and didn't do as well on those sections of Bio.
Some people are mathematical, they do better in Physics, Gen-Chem.
Some people are memorizers, they do well in O-Chem.
Of course, some people are just smart and good at everything.
This topic is an "eye of the beholder" situation.
BTW my worst grade in college... "The Diverse Worlds of Music"
How do you get an "A" in O-Chem and do crappy in a music class? Never go to class, never take any notes, never study. Sorry, but I fail to see how knowledge of African tribal music will help me as a doctor.
Damn liberal arts colleges with their gen-ed requirements!