Best for
Best for contact centres and outsourcers that want phone agents built, branded and launched under one contract.
- Enterprise
AI Voice & Speech Comparison
Synthflow vs. Vapi
At a glance
At a glance
Best for
Best for developers putting voice agents on real phone lines for support, lead qualification or scheduling.
- Small and mid-sized
- Enterprise
Cataleo does not name a winner. Both statements come from the vendors themselves.
Full Comparison
| Criterion | Synthflow | Vapi |
|---|---|---|
| Starting price | From $30,000 / year Enterprise contracts start there and are scoped around call volume, concurrency, telephony setup, integrations, security needs and launch support. No self-serve tier is published. | lower value From $0.05 / minute of calls Build plan, usage-based, plus $0.005 per SMS or chat message. Ten concurrent lines are included and further lines cost $10 / month each. Model provider costs for speech-to-text, the LLM and text-to-speech are passed through at cost, or nothing if you bring your own API keys. |
| Commercial use | Yes, under an enterprise contract | Yes, usage-based |
| Output | Voice and chat agents for inbound and outbound phone calls, including white-labelled agents resold under a partner's brand | Voice agents for inbound and outbound phone calls, web voice, and SMS or chat |
| API | Yes, a public Platform API, plus an MCP server for MCP-capable clients | Yes, REST API, CLI and SDKs |
| Hosting | Cloud, with region-based hosting | Not stated |
| Voice cloning | Cloning happens in ElevenLabs, not in Synthflow. The voice selector offers Synthflow's own TTS with twelve built-in voices and the ElevenLabs models from Turbo v2 and Flash v2.5 up to v3; a cloned or provider-specific voice is added through Imported > Import Voice by pasting the provider voice ID, or by connecting your own ElevenLabs API key so that account's custom voices appear in the selector. The vendor warns that a synthesiser model your own ElevenLabs plan lacks can mean lower quality or higher latency on your key | Not part of Vapi itself; voices come from connected providers such as ElevenLabs and Deepgram |
| Real-time use | Yes, live inbound and outbound calls, with IVR handling for outbound agents, voicemail and silence handling, in-call SMS and WhatsApp messaging, and WhatsApp Business calling. The vendor states 99.99% uptime on its own telephony infrastructure | Yes, live inbound and outbound phone and web conversations at an average latency under 500 ms |
| Languages | Over 30 languages are listed in the documentation, plus a multilingual mode that switches between English, Spanish, French, German, Hindi, Russian, Portuguese, Japanese, Italian and Dutch within a single call. Speech recognition runs on Deepgram or Synthflow's own engine, which the vendor recommends for non-English | Depends on the providers chosen for a given assistant: automatic language detection and code-switching with Deepgram (100+ languages), Google STT (125+) or Gladia (110+), while Azure, OpenAI Whisper, Speechmatics and Talkscriber run one language at a time; on the voice side Vapi's own voices cover 40+ languages, Azure 140+ and ElevenLabs 30+. The languages an assistant may use have to be listed in its system prompt |
| Speech-to-speech and dubbing | Not documented. The voice documentation covers text-to-speech for live agents, with a speaker and a synthesis model chosen per agent, and carries no speech-to-speech conversion and no dubbing | Yes, a call runs as spoken conversation by chaining speech-to-text, a language model and text-to-speech, with natural turn-taking |
| Editing and controls | Flow Designer, a node-based canvas with conversation, message, branch, jump and custom action nodes, or a simpler prompt builder, plus a multi-agent system for several flows behind one agent, voice model and pacing settings, manual testing, automated simulations and custom evaluations that score calls against business goals | Assistants for a single prompt with tools, Squads for multi-assistant orchestration, tool calls into APIs and databases mid-conversation, plus testing and call observability |
| Consent and trust | SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with encryption, audit logs and region-based hosting. Per-agent controls decide whether recordings and transcripts are kept at all, cap retention at 30 days, and redact personal data from transcripts, webhook payloads and logs | SOC 2, HIPAA and PCI compliance with SSO, OAuth and role-based access control; HIPAA is a $2,000 / month add-on and zero data retention $1,000 / month on both plans |
| MCP-ready | Yes | Yes |
| Deployment | Cloud (SaaS), Browser-based | Cloud (SaaS), Browser-based |
| Support | Email helpdesk | more entries Email helpdesk, Community forum |
| Onboarding | more entries Documentation and knowledge base, Personal consulting | Documentation and knowledge base |
| Company size | Enterprise | more entries Small and mid-sized, Enterprise |
| Integrations | HubSpot, Salesforce, Zapier, Cal.com, GoHighLevel, Twilio, Genesys, Avaya, Five9, Cisco, RingCentral | OpenAI, Anthropic, Groq, Deepgram, Gladia, ElevenLabs, Salesforce, HubSpot, Zapier, Slack, Google Workspace |
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The short version
Key Differences
- Starting price Synthflow From $30,000 / year Vapi From $0.05 / minute of calls
- Company size Synthflow Enterprise Vapi Small and mid-sized, Enterprise
- Support Synthflow Email helpdesk Vapi Email helpdesk, Community forum
- Commercial use Synthflow Yes, under an enterprise contract Vapi Yes, usage-based
- Output Synthflow Voice and chat agents for inbound and outbound phone calls, including white-labelled agents resold under a partner's brand Vapi Voice agents for inbound and outbound phone calls, web voice, and SMS or chat
Every line is one datapoint from the table above, picked automatically. Nothing here is written text.
The trade-offs
Strengths and Limitations
Synthflow
Strengths
- No-code Flow Designer with a multi-agent system, so a non-developer can build and change call flows
- Connects to existing telephony and contact centre stacks over SIP, including Genesys, Avaya, Five9, Cisco and RingCentral
- White-labelled deployments for partners reselling voice agents under their own brand
- SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with agent-level retention and PII redaction controls
Limitations
- No self-serve or trial tier is published; the only listed plan is an enterprise contract from $30,000 per year
- Pricing is scoped by sales, so the cost of a given call volume is not knowable from the website
- Latency figures differ between the vendor's own pages, so the published number is not a specification to rely on
- A cloned voice has to be created in a separate ElevenLabs account and imported, so it means a second subscription alongside Synthflow
Vapi
Strengths
- Per-minute pricing with model provider costs passed through at cost
- Bring your own provider keys and the pass-through drops to nothing
- Free choice of speech-to-text, model and voice provider across dozens of options
- Official MCP server lets external AI agents drive Vapi's APIs
Limitations
- HIPAA compliance and zero data retention are monthly add-ons rather than included
- Total cost depends on which model, transcription and voice providers you choose
- Concurrent lines beyond the first ten cost $10 per month each
- A platform to build on, not a finished call-centre product
Plans
Pricing
Synthflow
- Enterprise $30,000 Per year, the stated starting point. Scoped around call volume, concurrency, telephony setup, integrations and security needs, and covers implementation, onboarding, testing, training, launch support and ongoing optimisation, with SLA and support terms set in the contract.
Vapi
- Build $0.05 Per minute of calls, usage-based, plus $0.005 per SMS or chat message. Ten call concurrency included, additional lines $10 / month each. Model provider costs at cost. Community Discord and email support.
- Scale Not stated Annual contract with a fixed platform fee and committed volume, volume-based per-minute pricing on quote, enterprise features including SOC 2, HIPAA and PCI, a dedicated account team and a custom support SLA.
What users say
Review Scores · opens after launch
Synthflow
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Vapi
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Where this comes from
Where this comes from
Synthflow https://synthflow.ai · checked against the official source on 2026-09-13
Vapi https://vapi.ai · checked against the official source on 2026-08-30
This table lists factual criteria taken from information the vendors publish themselves. For how we put it together, see the methodology.