This study investigates music-related argumentation in different music genres (rock/pop versus classical music) applying a mixed-methods design with three groups (referred to as novices, semi-experts and experts). Participants were asked to compare two versions of a musical piece and justify their preference in individually written argumentation. Arguments were coded by applying a category system with four main categories, namely, attributes of the musical piece, subjective dimensions, context-specific background knowledge and media-related dimensions. Results of quantitative analyses showed that experts formulated longer arguments, referring to more different categories and mentioning more aspects within these categories. Further, a larger proportion of the experts' arguments referred to context-specific background knowledge and attributes of the musical piece, whereas semi-experts' and novices' argumentation consisted to a larger extent of subjective dimensions. For all analyses, there were no differences concerning the two different music genres. A discriminant analysis showed that the participants' ascribed level of expertise was correctly predicted on the basis of their argumentation in 97.3% of the cases. Therefore, the category system provides an effective instrument for representing and evaluating music-related argumentation. Our findings illustrate quantitative and qualitative differences between arguments and build a starting point for developing innovative intervention approaches for fostering music-related argumentation.