Retell AI vs Vapi

What is Retell AI?

Retell AI is an enterprise-grade conversational AI platform designed to automate telephone calls and call center workflows. It allows businesses and developers to create, deploy, and monitor realistic AI voice agents capable of conducting natural, two-way phone conversations. Powered by proprietary voice orchestration that manages speech recognition, LLM reasoning, and text-to-speech output, the platform delivers smooth conversation pacing with approximately 600ms latency and native turn-taking that handles mid-sentence interruptions.

What is Vapi?

Vapi is a specialized voice AI orchestration platform designed specifically for engineering teams and developers who need to build high-performance conversational agents. The platform serves as a unified API layer that connects Speech-to-Text (STT), Large Language Models (LLMs), and Text-to-Speech (TTS) technologies. By abstracting the complex infrastructure required for real-time audio, Vapi allows developers to focus on crafting conversation logic while the platform handles the low-latency transport and synchronization necessary for human-like interactions.

Who Retell AI is for

• Healthcare clinics can deploy voice agents to automate patient appointment scheduling, reduce phone tag, and improve NPS while complying with HIPAA.
• Contact center managers can automate high-volume tier-1 customer inquiries and leverage agentic transfers to brief live agents before handing off calls.
• Collections agencies can handle inbound billing inquiries and execute outbound reminder campaigns at scale to improve recovery rates.

Who Vapi is for

• Logistics engineering teams can automate inbound shipping inquiries and job bookings to save hundreds of manual hours.
• Healthcare developers can build secure, HIPAA-compliant voice assistants to manage patient appointment scheduling.
• Fintech companies can deploy voice agents to handle customer service calls with PCI-compliant data handling.

Retell AI features

• Hipaa, soc 2 type ii, gdpr, and iso 27001 compliance
• Omnichannel support covering voice, sms, chat, and API
• Interactive ivr navigation and dtmf digit dialing
• Outbound calling campaigns with automated pacing and retry management
• Agentic human handoffs with context briefing
• Drag-and-drop visual conversation builder
• Proprietary turn-taking with mid-sentence interruption handling
• Ultra-low conversational latency (~600ms)

Vapi features

• Multilingual support (100+ languages)
• Telephony and sip integration
• A/b experimental testing
• Automated hallucination testing
• Real-time tool calling
• Bring your own keys (byok) support
• API-native configuration
• Sub-500ms low-latency audio

Retell AI strengths

• Achieves around 600ms response latency for realistic, conversational speech flow.
• Pay-as-you-go pricing requires no annual contract and includes $10 in trial credits.
• Extensive choice of models, including leading LLMs from OpenAI, Anthropic, and Google, plus multiple TTS engines.
• Built-in call center capabilities like IVR navigation, outbound campaign scheduling, and live intervention.

Vapi strengths

• Achieves sub-500ms latency for near-instant voice responses.
• Supports a wide range of model providers including OpenAI, Anthropic, and Deepgram.
• Offers robust security compliance including SOC2, HIPAA, and PCI.
• Provides developers with over 1000 configuration points via a flexible API.

Retell AI limitations

• Pay-as-you-go plan is capped at 20 concurrent calls without upgrading or requesting more on demand.
• Advanced enterprise features like dedicated servers and implementation assistance require paid add-ons or custom contracts.

Vapi limitations

• Standard call history is limited to only 14 days on the pay-as-you-go plan.
• HIPAA Zero Data Retention compliance requires a high monthly add-on fee of $1,000.
• Users are charged for model provider costs 'at cost' on top of Vapi hosting fees.
• Requires significant developer expertise to set up and manage the API-first architecture.