I always love database optimization topics. Let me get some popcorn 
.
There are some real geeks 
out here. I’m not one of them. But I just had a good nap so let me blurt out my 2 cents:
Go with option A.
I had a project with option B and I ran into a bunch of limitations whenever I wanted to find something “the other way”.
For example, I had a building with a list of apartments. Fine if I started from the building. Whenever I started a search from the apartment side, it felt heavy to make the search criteria and to load the results.
Yes, I used the verb “to feel”. Not a scientific approach.
Also, option A is how @joe5 advised me to do it. Apparently lists are fine when they have a limited amount of items. After 100 (?), performance goes down.
There is a long thread by josh about this: Performance Q&A guide