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AI voice agent alternatives, compared honestly
Vapi, Retell AI, Synthflow and Smith.ai are strong services. Here is who each one suits, how Narvin differs, and how to choose for a UK business.
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Narvin vs Vapi
Vapi is a developer-first voice AI platform. Teams define assistants through its API and dashboard and choose their own speech, model and voice providers. Pricing is usage-based in US dollars, with provider costs depending on the stack you choose.
Read the comparisonNarvin vs Retell AI
Retell AI is a voice agent platform with an API and a visual builder for conversation flows. It is popular with developers and agencies, with usage-based pricing in US dollars.
Read the comparisonNarvin vs Synthflow
Synthflow is a no-code voice AI platform aimed at businesses and agencies, including white-label options. Plans are priced in US dollars.
Read the comparisonNarvin vs Smith.ai
Smith.ai offers two services: live virtual receptionists staffed by its own agents, and an AI receptionist that can escalate calls to those agents. Both are priced per call in US dollars, with add-ons for features such as booking and live involvement.
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In one line
Who each platform is for
| Platform | Built for |
|---|---|
| Narvin | UK small and mid-sized businesses and the teams that run their phones |
| Vapi | Developers and product teams building voice applications |
| Retell AI | Developers, agencies and technical teams |
| Synthflow | Businesses and agencies, including white-label resellers |
| Smith.ai | Small businesses and professional firms, especially in North America |
Buyer’s guide
How to choose an AI voice agent platform
Four questions that separate a good fit from an expensive mistake.
Who will build and run the agent?
Developer platforms give you a toolkit: you choose speech, model and voice providers, write the logic and host your own tools. That is powerful if you have engineers and want full control.
Business platforms such as Narvin give you working agents out of the box — templates, a knowledge base, integrations and call logs — so an office manager can change the script without a developer.
How does the price add up?
Compare the whole monthly cost, not just a headline per-minute rate. Some platforms bill model, voice, transcription and telephony separately, in US dollars. Narvin charges a monthly plan (from £0) plus usage at typically £0.42 per minute, in pounds.
- Platform or plan fee
- Per-minute usage, and what it includes
- Phone number and carrier charges
- Currency and VAT
- Onboarding or support fees
Which channels do you need?
If you only need inbound calls, most platforms will do. If you also want web chat, a voice widget on your site and outbound campaigns with calling windows and outcome tracking, check that they come from one agent and one dashboard rather than separate products.
Where does your data live, and who can see it?
UK businesses should ask about data location, sub-processors, retention controls, recording consent and whether a Data Processing Agreement is available. For outbound calling, check how the platform helps you respect PECR and the TPS register.
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