In a comprehensive comparison between ElevenLabs Agents and OpenAI's Realtime API for conversational agents, several key differences are highlighted to guide developers in choosing the right platform. ElevenLabs Agents, rebranded and expanded with major releases, use a modular architecture that integrates Speech to Text, LLM, and Text to Speech components, offering superior performance in function-calling accuracy, instruction following, and reasoning compared to OpenAI. It provides a more reliable and customizable voice experience with a vast library of over 5,000 voices and supports multi-agent workflows, making it suitable for complex business scenarios. ElevenLabs' platform excels in testing with text-based evaluations, integrated analytics, and broader telephony capabilities, including native integrations and outbound calling features. In contrast, OpenAI's Realtime API, with its integrated speech-to-speech model, emphasizes low latency and dynamic voice adaptation, making it more suitable for prototypes and personal applications despite its limitations in flexibility and output consistency. Pricing strategies differ, with ElevenLabs offering competitive rates for high-volume production use, while OpenAI's token-based pricing may suit simpler prototype needs.