Parloa for contact-center calls. Sierra for branded multi-channel. Vapi for developer-built voice agents.
These three names dominate AI voice in 2026. Each one wins a specific buyer profile. This guide breaks down which to pick on volume, channel mix, and engineering capability.
The 30-second comparison
| Parloa | Sierra | Vapi | Decagon (voice) | Intercom Fin (voice) | |
|---|---|---|---|---|---|
| Best for | Contact-center voice | Branded voice + chat parity | Developer-first builds | Chat-first w/ voice secondary | Intercom users adding voice |
| Pricing | Enterprise contracts $60–120K/yr | Enterprise $150–500K/yr | $0.05/min PAYG | Per-resolution | Per-resolution |
| Latency | Under 800ms | Under 900ms | Under 1s (depends on stack) | N/A primary | Newer / less mature |
| Languages | 12+ with native voices | 100+ | LLM-dependent | English-primary | English-primary |
| Setup time | 4–8 weeks | 4–12 weeks | DIY (engineering-led) | Hours-days for chat, weeks for voice | 1–2 weeks |
| Best feature | Native telephony + handoff | Brand consistency | SDK + cost transparency | Chat parity | Outcome pricing |
All five run on the voice capability — real-time speech understanding + generation, with sub-second latency for natural conversation.
When each one wins
Pick Parloa for tier-1 contact center calls
Parloa is the leader for voice-first contact center deployments. Native integration with Twilio, Vonage, and Genesys. Latency under 800ms (the threshold where calls feel natural). 12+ languages with studio-trained voices.
Real deployments handle 50–65% of tier-1 calls without human intervention. Handoff to human agents preserves full transcript + intent classification.
Use cases:
- High-volume B2C support
- Order status, account lookup, simple FAQ
- Multi-language contact centers
- Outsourced support replacement
Pick Sierra for branded voice that mirrors chat
Sierra is the choice when voice and chat must feel like the same persona. Both channels use the same brand voice, knowledge base, action handlers. A customer who switches from chat to voice mid-conversation gets continuity.
Best for premium consumer brands where CX is a differentiator. Enterprise pricing ($150–500K/year).
Pick Vapi for developer-built voice agents
Vapi is the SDK-first option. Pay-as-you-go at $0.05/minute. Bring your own LLM (Anthropic, OpenAI, custom). You build the conversation logic; Vapi handles the voice plumbing — speech-to-text, LLM call, text-to-speech, telephony, turn-taking.
Use cases:
- Custom voice agents for niche workflows
- Engineering-led organizations
- Cost-sensitive deployments at moderate volume
- Voice features in your own SaaS product
Pick Decagon if you want chat-primary with voice add-on
Decagon is chat-first but added voice in 2025. Best if you've already deployed Decagon for chat and want voice as a secondary channel — not the leading voice provider for new deployments.
Pick Intercom Fin if voice rolls out of your existing Intercom
Intercom Fin voice is the natural add-on for Intercom customers. Outcome-based pricing carries over (~$1/resolution). Setup is fast because the integration is already there.
Less competitive on call latency and language coverage than Parloa, but the deployment story is much simpler.
Voice quality: what matters in 2026
Three dimensions to evaluate:
1. Latency. Sub-800ms is the natural-conversation threshold. Past 1s the call feels like talking to a slow IVR. Parloa and Sierra are both under 800ms. Vapi depends on your LLM choice.
2. Naturalness. AI voices in 2026 are very close to indistinguishable on short utterances. The remaining tells: too-consistent pacing, no genuine "umm" / throat-clear, slight over-formality. ElevenLabs voices (used by many of these platforms) lead on expression.
3. Recovery. When the customer says something unexpected — accent, background noise, mumbled words — how does the agent handle it? The best platforms ask clarifying questions naturally. The worst loop into "I didn't quite catch that" repeatedly.
Specific workflow recommendations
| Workflow | Pick |
|---|---|
| Inbound support, high volume | Parloa |
| Branded consumer voice + chat | Sierra |
| Custom voice agent in your product | Vapi |
| Order status / appointment IVR replacement | Parloa or Vapi |
| Outbound sales calls | Vapi (custom build) or specialized vendors |
| Multi-language voice (12+ languages) | Parloa |
| Adding voice to existing chat deployment | Intercom Fin (if Intercom) or Decagon |
Deflection rate reality
Realistic voice deflection in 2026:
| Use case | Tier-1 deflection |
|---|---|
| Order status / FAQ | 70–85% |
| Account lookups | 60–75% |
| Simple intent routing | 80–90% |
| Refund / cancellation flows | 45–60% |
| Complex billing disputes | 20–35% |
| Anything requiring empathy | 15–30% |
Voice deflection lags chat by 10–15 percentage points on average. Calls have more ambiguity (accents, background, tone) than text. Plan for 60–70% on average tier-1 mix.
Pricing reality
| Tier | Volume | Annual cost | Per-call cost |
|---|---|---|---|
| Vapi PAYG | 10K min/mo | ~$6K | ~$0.30/3-min call |
| Parloa mid | 50K calls/mo | $60–100K | $0.10–0.17 |
| Parloa enterprise | 200K calls/mo | $200–500K | $0.08–0.20 |
| Sierra mid voice | 50K calls/mo | $150–250K | $0.25–0.40 |
| Sierra enterprise | 200K calls/mo | $400–800K | $0.16–0.33 |
Sanity check vs human: a US-based call-center rep fully loaded costs $40–60K/year and handles ~6,000 calls/year — about $7–10/call. Even Sierra's enterprise tier at $0.30/call is 20× cheaper.
Build vs buy
For most teams: buy. Parloa or Sierra ship with battle-tested infrastructure (telephony, latency, language coverage, compliance) that's hard to replicate from scratch.
Build with Vapi when:
- Your use case is so specific that no vendor's prompts fit
- You have a small but persistent voice-AI use case (under 50K min/month)
- Cost transparency matters more than convenience
- You're embedding voice AI inside your own SaaS product
What about ElevenLabs?
ElevenLabs isn't a voice agent platform — it's the voice synthesis layer that powers many of them. If you build with Vapi (or your own stack), ElevenLabs is likely the voice provider you wire in.
For standalone voice creation (narration, dubs, ads, podcasts) ElevenLabs is the right tool. For full conversational agents that take action, you need an agent platform on top.
The verdict
For enterprise contact centers: Parloa.
For branded multi-channel CX: Sierra.
For developer-built voice: Vapi.
For adding voice to existing Intercom: Intercom Fin.
If you're not sure where to start: test Vapi for one workflow at $50/month of credits. You'll learn what you actually need before signing a multi-year enterprise contract.
For broader support agent options see our customer support agent buyer's guide and the /category/support catalog.