In recent years, the get-big-fast strategy of platform network management is increasingly challenged, while the research focusing on network collaboration has made great progress. The exploration of paradigms and their applicable contexts behind these two types of theories can contribute to complete understanding of the operation rules of network platform. This paper abstracts two-sided market paradigm and system competition paradigm from these theories abovementioned. The former emphasizes the expansion of platform network scale through cross-network effects; the latter underlines the creation of the end-user value by coordinating the network operation. Through a comparative analysis of two C2C platforms, i.e. TAOBAO and YIQU, and two SAAS platforms, i.e. ALISOFT and 800APP, this paper induces the applicable conditions of these two paradigms: the two-sided market paradigm is suitable for the context with low network complexity and high platform competition intensity, while the system competition paradigm is suitable for the context with high network complexity and low platform competition intensity. By building a network growth model taking platform network size and network synergy into account, this paper explains the reasons for success or failure in a specific platform management paradigm in specific contexts, and thus integrates these two paradigms in a single theoretical framework, deepening the understanding of platform network. From the view point of practice, the identification of applicable conditions of different paradigms helps to enhance the suitability of platform management decisions.