Stellar vs Synthflow
Stellar vs Synthflow: Transparent Pricing and Consistent Voice Quality
Synthflow and Stellar both offer no-code voice agent builders, which makes this a closer comparison than most. The key differences come down to three things: pricing transparency, voice consistency, and focus. Synthflow does not publish pricing on their website, so you are negotiating before you know what it costs. Their voice quality varies because they route through different TTS providers depending on configuration. Stellar publishes every plan and rate on the pricing page, uses a single speech-to-speech model (GPT Realtime) for consistent quality, and focuses on three high-value workflows rather than trying to be everything.
The verdict
Synthflow targets agencies with white-label features. Stellar targets businesses that want to deploy fast with predictable costs. If you are reselling voice AI to clients, Synthflow has tools for that. If you want to run your own agents without surprises on the invoice, Stellar is the better fit.
Where Stellar wins
- Published pricing on the website. 14-day free trial, three paid plans, per-minute rates all visible before signup.
- Consistent voice quality through GPT Realtime, a single native speech-to-speech model.
- Purpose-built templates for lead qualification, appointment booking, and event confirmation.
- SOC 2 compliant with TCPA safeguards included on every plan.
- Knowledge base with vector search: upload your docs and the agent answers from them.
Where Synthflow wins
- White-label capabilities let agencies resell under their own brand.
- Broader range of voice providers gives more accent and language options.
- Agency-focused features like client workspaces and multi-tenant management.
Pricing compared
Stellar's pricing is public: 14-day free trial, then Growth at $149/mo (200 min included, $0.18/min overage), Pro at $399/mo (750 min included, $0.14/min overage), Scale at $899/mo (3,000 min included, $0.11/min overage). Synthflow requires you to contact their sales team before seeing any numbers. For businesses that want to evaluate cost before committing to a demo call, this matters. Some Synthflow users report that final pricing ends up higher than expected after factoring in add-ons and overages.
Switching from Synthflow
Moving from Synthflow to Stellar is straightforward. Export your conversation scripts, then rebuild them using Stellar's template builder. Most configurations map directly. Phone numbers are portable. Plan for about an hour of setup per agent.
Read the Synthflow alternative guideStellar vs Synthflow: FAQ
Is Synthflow better for agencies?
If you are reselling voice agents to multiple clients under your own brand, Synthflow's white-label features are a real advantage. Stellar does not offer white-labeling today. For businesses deploying agents for their own use, Stellar's focused templates and transparent pricing make more sense.
Why does voice consistency matter?
When your AI agent sounds different from call to call (different accent, different pacing, different tone), it erodes trust. Synthflow routes through multiple TTS providers, which means voice quality can shift depending on load and configuration. Stellar uses one model, GPT Realtime, for every call. Same voice, same quality, every time.
Does Stellar support multiple languages?
Stellar supports English today, with additional languages on the roadmap. Synthflow offers more language options through its multiple voice providers. If multilingual support is a hard requirement right now, that is worth factoring in.
Can I try Stellar before paying?
Yes. Every new account gets a 14-day free trial of Growth (3 agents, 200 minutes, every integration), no credit card required. You can build a full agent, test it with real calls, and only upgrade once you're sure it works for your business.
Try Stellar free for 14 days
Full Growth-plan access. No credit card required.