Ethically relevant differences are aspects of context or facts of the matter that shift the values that we think to be applicable to deciding a course of action. These are essential in determining whether or not justice has been achieved in that particular situation.
For example, there could be two patients who are clinically very similar, but one lacks capacity and the other does not. The difference in decision making capacity between the two means that respect for autonomy will be less important in both the content and form of decision making for the patient who lacks capacity, such that a best interests standard is much more likely to be applied (and we see this reflected in guidelines around decision making with infants and children).
Other ethically relevant differences might be resource constraints; decisions made about care during times of crisis (higher demand) or shortages (reduced supply) are not expected to be the same as those made during times when it is “business as usual”.