This chapter explores the notion of advantage, which is key in State aid law. To qualify a measure as State aid, an advantage should be established, that is, an economic benefit that an undertaking would not have obtained in the absence of State intervention. The notion of advantage crystallizes the distinct and complex issues raised in State aid law and reflects the difficulties in assessing a sound balance between political interest, economic constraints, and legal requirements. In this regard, the intervention of public authorities in economic transactions or the support for services of general interest is one of the ever-growing areas which leaves room for debate. The chapter then looks at the subtle issues of the market economy operator test and the services of public interest.