Feeling like double postings, so I will respond to this one.
I don't have any relationship to UC schools, but I don't think which class to take will matter at all.
You might get benefits from these classes for MCAT / later medical schools anyway.
If you don't take a class because you are afraid that it's hard, medical schools can be much harder than you can ever imagine.
So if I was you, I would just choose from them randomly.
However, in your other post you say that "x105" is an online course.
I will prefer x115 because some schools may have some bias to online courses. (although it may not be a problem if it's taught in an accredit institution.)