The evolution of Large Language Models (LLMs) has given rise to two prominent methods for managing extensive contextual information: Retrieval-Augmented Generation (RAG) and Long-Context (LC) LLMs. RAG enhances responses by integrating external, up-to-date data, making it beneficial for tasks requiring current or domain-specific information, yet it relies heavily on the quality of retrieved data, which can introduce noise if not managed properly. LC LLMs, by contrast, process long text sequences within their architecture, allowing for more comprehensive understanding without the need for external systems, although they can be computationally expensive and face challenges like the "lost in the middle" phenomenon, where mid-sequence information may be overlooked. Hybrid approaches, such as SELF-ROUTE, dynamically select between RAG and LC based on task needs, optimizing performance and cost. Real-world applications of these models span sectors like healthcare, finance, legal, and marketing, each benefiting from the strengths of RAG and LC LLMs. Future research is directed towards refining these methodologies to address existing limitations and improve performance, particularly in long-context scenarios where LC models excel but at a higher computational cost.