VAPI vs Retell AI vs LiveKit vs Bland AI:
Voice AI Platform Comparison 2026

TL;DR — Which Platform Should You Choose?

VAPI is the most developer-friendly managed voice AI platform. Configure an assistant with a system prompt, pick your STT/LLM/TTS providers, connect a phone number, and you're live in hours. VAPI handles WebRTC, SIP, noise cancellation, turn detection, and TTS streaming — everything as a managed service.

curl -X POST https://api.vapi.ai/assistant \
  -H "Authorization: Bearer $VAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Support Bot",
    "model": { "provider": "openai", "model": "gpt-4o",
      "systemPrompt": "You are a helpful support agent. Be concise." },
    "voice": { "provider": "elevenlabs", "voiceId": "YOUR_VOICE_ID" },
    "transcriber": { "provider": "deepgram", "model": "nova-2" },
    "firstMessage": "Hello! How can I help you today?"
  }'

LiveKit Agents SDK is fully open-source (Apache 2.0) and self-hostable. You write Python or Node.js agent code, plug in any STT/LLM/TTS, and run it on your own infrastructure. There is no per-minute fee — you pay only for server costs. LiveKit is the only platform where full HIPAA compliance is possible without an enterprise contract.

from livekit.agents import AutoSubscribe, JobContext, WorkerOptions, cli
from livekit.agents.voice_assistant import VoiceAssistant
from livekit.plugins import deepgram, openai, elevenlabs, silero

async def entrypoint(ctx: JobContext):
    await ctx.connect(auto_subscribe=AutoSubscribe.AUDIO_ONLY)
    assistant = VoiceAssistant(
        vad=silero.VAD.load(),
        stt=deepgram.STT(model="nova-2"),
        llm=openai.LLM(model="gpt-4o"),          # Swap any OpenAI-compatible endpoint
        tts=elevenlabs.TTS(voice_id="YOUR_ID"),
        allow_interruptions=True,
    )
    assistant.start(ctx.room)
    await assistant.say("Hello! How can I help?")

cli.run_app(WorkerOptions(entrypoint_fnc=entrypoint))

Retell AI takes simplicity further than VAPI — define an agent, pick a voice, connect a phone number, and you're live. Retell is particularly strong for outbound calling campaigns: bulk dial lists, scheduling, analytics, and A/B testing call scripts. The custom LLM server option gives some flexibility, but you still route through Retell's infrastructure.

# Create agent
curl -X POST https://api.retellai.com/create-agent \
  -H "Authorization: Bearer $RETELL_KEY" \
  -d '{
    "agent_name": "Appointment Bot",
    "voice_id": "11labs-Adrian",
    "response_engine": { "type": "retell-llm",
      "llm_id": "YOUR_LLM_ID" },
    "begin_message": "Hi, this is Sarah calling to confirm your appointment."
  }'

# Trigger outbound call
curl -X POST https://api.retellai.com/create-phone-call \
  -H "Authorization: Bearer $RETELL_KEY" \
  -d '{ "from_number": "+12025550100",
        "to_number": "+19175550199",
        "agent_id": "YOUR_AGENT_ID" }'

Bland AI targets large enterprise outbound calling operations — think 10,000+ calls per day. It offers dedicated infrastructure (no shared queue), ultra-realistic proprietary voices, built-in CRM integrations (Salesforce, HubSpot), and enterprise SLA guarantees. Bland is the platform when you're running massive outbound campaigns for insurance, healthcare reminders, or collections.

curl -X POST https://api.bland.ai/v1/calls \
  -H "Authorization: Bearer $BLAND_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "phone_number": "+19175550100",
    "task": "You are calling to confirm appointment on April 20th at 2pm. If they need to reschedule, collect their preferred time and update the CRM.",
    "voice": "maya",
    "max_duration": 5,
    "record": true,
    "webhook": "https://yourdomain.com/bland-webhook"
  }'

Full Feature Comparison Matrix

Every key decision criteria across all four platforms in a single table. Green = advantage, grey = neutral or partial, red = disadvantage.

Latency Comparison: Which Platform Is Fastest?

End-to-end latency is the time from when the caller stops speaking to when they hear the bot's first audio byte. Callers tolerate up to 700ms — beyond that, it feels unnatural. Latency is driven by both the platform and your STT/LLM/TTS choices. All figures assume Deepgram Nova-2 + GPT-4o + ElevenLabs Turbo with streaming enabled.

Pricing Comparison at Scale

Platform fees only — excludes STT, LLM, and TTS API costs which apply equally across managed platforms. LiveKit server costs assume a $200/month 8-vCPU server handling 50K min/month comfortably.

Decision Guide: Which Platform for Your Use Case?

10 real-world scenarios mapped to the right platform choice.

SIP & Asterisk Integration: Platform by Platform

All four platforms support real phone calls via SIP/PSTN. Here's how each integrates with your existing Asterisk or FreeSWITCH infrastructure:

; pjsip.conf
[voice-ai-bot]
type=endpoint
transport=transport-tls                    ; Use TLS for security
context=from-voice-ai
disallow=all
allow=ulaw
allow=alaw
aors=voice-ai-bot-aor
outbound_auth=voice-ai-auth

[voice-ai-bot-aor]
type=aor
contact=sip:sip.PLATFORM_ENDPOINT:5060    ; Replace with VAPI/LiveKit/Retell URI

; extensions.conf — route DID to voice AI bot
[from-pstn]
exten => +12025551234,1,NoOp(Route to AI Bot)
 same => n,Answer()
 same => n,Dial(PJSIP/+12025551234@voice-ai-bot,120,TtKk)
 same => n,Hangup()

Platform Recommendations by Industry

Based on 25+ voice bot deployments, these are the platform-industry combinations that work best in production:

Frequently Asked Questions