GPT-Live vs ElevenLabs Conversational vs Retell for Voice Agents (July 2026)
The Landscape (July 12, 2026)
| Platform | Full-duplex | Telephony (SIP/PSTN) | API today? | Best for | Rough $/min |
|---|---|---|---|---|---|
| GPT-Live-1 | ✅ | ❌ | ❌ (ChatGPT only) | Consumer voice UX inside ChatGPT | Included in plan |
| ChatGPT Realtime API | ⚠️ Partial | Via 3rd party | ✅ | Custom voice apps needing OpenAI models | ~$0.30/min |
| ElevenLabs Conv. AI | ✅ | Via 3rd party | ✅ | Web/app agents needing best voices | $0.10-0.20 |
| Retell | ✅ | ✅ Native | ✅ | Outbound/inbound phone agents | $0.05-0.15 |
| Vapi | ✅ | ✅ Native | ✅ | Developer-first phone agents | $0.05-0.10 |
| Bland | ✅ | ✅ Native | ✅ | High-volume outbound calls | $0.09 |
| Gemini Live API | ⚠️ | Via 3rd party | ✅ | Voice + vision + screen share | Varies |
| Cartesia Sonic | ✅ (as TTS) | Via 3rd party | ✅ | Ultra-low-latency TTS engine | $0.02-0.05 |
Decision Tree
”Where does the voice live?”
- In a phone call (inbound support, outbound sales, appointment reminders) → Retell / Vapi / Bland
- In a web or mobile app (in-product chat, tutoring, coaching) → ElevenLabs Conversational AI or ChatGPT Realtime API
- Inside ChatGPT (no custom app) → GPT-Live (July 8, 2026 launch)
- Multimodal (audio + vision) → Gemini Live API
”How much control do I need?”
- Full control over LLM, prompt, tools → Retell, Vapi, ElevenLabs, Realtime API (all let you plug in your own model)
- Just want a voice with a persona → Bland (opinionated, less customization)
- Just want to use ChatGPT → GPT-Live
”What’s my volume?”
- <1000 min/mo → any platform is fine, pick on feature fit
- 10k-100k min/mo → cost matters; Bland or Vapi typically win
- 100k+ min/mo → negotiate directly with the platform; Retell and ElevenLabs offer enterprise pricing
The Full-Duplex Baseline
As of July 2026, full-duplex is the assumed baseline for any voice-agent product. That means:
- Interrupt handling (user cuts in, agent stops)
- Backchanneling (agent’s “uh-huh”s during user speech)
- Barge-in recovery (rejoining smoothly after interruption)
Any voice platform that’s still turn-based in July 2026 is behind. Every option in the table above supports full-duplex.
Latency Reality Check
Sub-500ms end-to-end (mouth-to-ear) is what feels human. Here’s what platforms actually deliver:
| Platform | Real-world median | Median floor |
|---|---|---|
| ElevenLabs Conv. AI | 350-500ms | 300ms |
| Retell | 400-600ms | 350ms |
| Vapi | 400-700ms | 350ms |
| Bland | 500-700ms | 400ms |
| Cartesia Sonic (TTS) | 100-150ms (TTS only) | 90ms |
| OpenAI Realtime API | 300-500ms | 250ms |
| GPT-Live inside ChatGPT | 300-400ms | 250ms |
Real-world latency depends heavily on: LLM inference time (biggest variable), network hop count, whether you’re using GPT-4o-mini vs Claude Haiku 4.5 vs GPT-5.6 Luna under the hood. Cartesia Sonic is a TTS engine — pair it with a fast LLM for lowest total latency in custom stacks.
What Each Platform Is Best At
ElevenLabs Conversational AI
- Best voices in the market as of July 2026
- Voice cloning (30 seconds of source audio)
- Fine-grained prosody control (pitch, pace, emotion)
- SDK for JS, Python, Swift, Kotlin
- Weakness: telephony requires third-party (Twilio/Vonage)
Retell
- Native SIP / PSTN for phone-based agents
- Warm transfer to humans, IVR trees, TCPA compliance
- Salesforce, HubSpot, Zapier connectors
- Call analytics (sentiment, keywords, script adherence)
- Weakness: less voice customization; usually pairs with ElevenLabs
Vapi
- Developer-first — clean SDK, MCP tool support, web hooks
- Bring your own LLM, TTS, STT
- Reasonable telephony via Twilio
- Weakness: less turnkey than Retell for non-developer teams
Bland
- Cheapest at $0.09/min all-in
- Optimized for high-volume outbound (dialing thousands of calls)
- Less customization by design
- Weakness: less LLM/prompt control
GPT-Live (once API lands)
- Best conversational feel in the market
- Reasoning delegation to GPT-5.5 built in
- Weakness: no API yet as of July 12, 2026
The Bet for Q4 2026
Once GPT-Live API ships, expect ~30-40% of new voice-agent starts to build on it directly, another 30% to ship via Vapi/Retell/ElevenLabs orchestrators that pipe GPT-Live under the hood, and the rest to stay on their current stacks for lock-in reasons.
If you’re starting now: build on Retell (phone) or ElevenLabs (web), design the LLM layer to be swappable, and plan a Q1 2027 swap to GPT-Live if the API pricing comes in reasonably. Do not wait for GPT-Live API to start — you’ll lose two quarters of iteration.
Sources
- OpenAI GPT-Live announcement: OpenAI unveils voice AI GPT-Live (July 8, 2026)
- Retell docs: Retell.ai documentation
- ElevenLabs Conversational AI: elevenlabs.io/conversational-ai
- Vapi developer docs: docs.vapi.ai