"Competition on the merits" is a popular but vague term. The principles underlying it and any standards that are based on it need to be clarified.

The concept of "competition on the merits" is supposed to be a helpful point of reference for distinguishing unilateral conduct that is harmful to competition from unilateral conduct that enhances competition. Lawyers, judges and competition law enforcement officials have been using this phrase for many years to explain and justify their arguments "unreasonable," "improper," and "level playing field." The continued use of these terms despite the absence of precise, generally accepted definitions for them has led to inconsistent interpretations, and therefore to unpredictable results. Consequently, these phrases have not helped to promote a better understanding of the law and policy on abuse of dominance. There is a need for a more principled and consistent basis for determining liability in unilateral conduct cases.

https://www.oecd.org/competition/abuse/35911017.pdf