The article presents a comparative analysis of the Clean Architecture and Vertical Slice Architecture (VSA) approaches in the context of designing enterprise .NET applications, conducted from the vantage point of their evolutionary interplay, organizational applicability, and impact on maintainability. The study's relevance is that the .NET ecosystem remains one of the most robust corporate development standards. At the same time, the rising cost of change and the acceleration of DevOps cycles demand architectures that simultaneously sustain the resilience of the domain model and enable high-velocity feature delivery. The objective is to identify patterns of complexity distribution across layers and functional slices, and to formulate criteria for selecting or combining the specified approaches at different stages of the software system's life cycle. The novelty lies in the synthetic consideration of Clean Architecture and Vertical Slice Architecture not as mutually exclusive but as mutually complementary architectural paradigms, joined within a single spectrum of product maturity. It is recorded that both approaches implement different phases of the corporate solution life cycle: vertical slices prevail in the early stages, providing rapid adaptation and feedback, whereas as the product and organizational complexity grow, the role of Clean Architecture increases, ensuring the consistency and durability of solutions. The key conclusion is that an optimal strategy for enterprise .NET systems is a hybrid configuration in which Clean Architecture defines the systemic core and standardized interaction boundaries. At the same time, Vertical Slice Architecture shapes the peripheral modules responsible for the independent evolution of functional areas. In addition, it is established that the effectiveness of the chosen architecture is determined not by the pattern itself but by the engineering maturity of the team, the presence of automated tests, review procedures, and quality metrics, without which the advantages of both models are neutralized. The article is of practical value to software architects, technical leads, and researchers designing enterprise solutions on the .NET platform and seeking optimal strategies to balance stability and the speed of change.