Two domFis arguing over conflicting deeply-held beliefs -- oooh! I envision it being intensely heated for until both parties get their feelings hurt, and then it turns into a cold war, with neither side making a huge deal out of not speaking to each other.
My flatmate and I started off walking on eggshells around each other, and then (over the course of an year) we were the great friends for a while, and then we pissed each other off a lot, and now we're back to being guarded around each other and not making a big deal out of not speaking much to each other.
It was only a few months ago that I chalked it down to the conflicting Fi. Too much ISFP in one flat.
Back to the OP, xSFJ vs xSFJ on how to arrange the furniture in their new flat. They hold radically different views.