Side-by-side comparison · Sales & Customer Support
Reply.io vs Retell AI vs Sierra
Everything that matters when choosing between them, in one place: our rating, what each can do, what they cost, and the trade-offs.
Comparing 3 tools, the maximum.
At a glance
Pick it if: Small sales teams, founders and agencies running cold email and LinkedIn outreach.
Pick it if: Service businesses and agencies that want an AI receptionist or phone agent without hiring developers.
Pick it if: Large consumer brands that want an AI agent to handle a big share of their customer conversations end to end.
Overview
| Attribute | Reply.io | Retell AI | Sierra |
|---|---|---|---|
| In one line | Cold email and LinkedIn outreach sequences, plus an AI SDR that writes and replies. | AI phone agents that answer calls, book appointments and make outbound calls. | Builds and runs AI customer service agents for big brands, across chat, email and phone. |
| Pricing model | Paid | Paid | Paid |
| Starting price | From $49/user/mo | About $0.07–$0.31/min | See website |
| Free plan | No | No | No |
| Works with Claude Code | Yes | Yes | No |
Rating breakdown
Our scores out of 5. The higher bar in each row is highlighted.
| Attribute | Reply.io | Retell AI | Sierra |
|---|---|---|---|
| Overall rating | 3.7 | 4.1Winner | 3.9 |
| Ease of useHow quickly someone non-technical gets value from it. | 4.0 | 3.5 | 3.0 |
| FeaturesHow completely it covers its own job, and how well the pieces fit together. | 4.0 | 4.5 | 4.5 |
| Output qualityHow good the results are before you fix them. | 3.5 | 4.5 | 4.5 |
| Value for moneyWhat you get for the price, including the free plan. | 3.5 | 4.0 | 3.0 |
| Speed & reliabilityHow fast it is and how often it falls over. | 3.5 | 4.0 | 4.5 |
Feature comparison
A tick means it does this today. A dash means we haven't checked.
| Attribute | Reply.io | Retell AI | Sierra |
|---|---|---|---|
| Access & platform | |||
| Free plan | No | No | No |
| Mobile app | – | – | – |
| Desktop app | – | – | – |
| Browser extension | Yes | – | – |
| API access | Yes | Yes | – |
| Teams & business | |||
| Team workspace | Yes | Yes | Yes |
| Enterprise plan or SSO | – | Yes | Yes |
| Connects to other apps | Yes | Yes | Yes |
| Open source or self-hosted | No | No | No |
| AI abilities | |||
| Works with your files | – | Yes | Yes |
| Understands images | – | – | – |
| Makes images | No | No | No |
| Makes video | No | No | No |
| Writes code | – | – | – |
| Runs agents or automations | Yes | Yes | Yes |
| Learns your brand or style | – | – | Yes |
| Works in many languages | Yes | Yes | Yes |
| Capabilities score | 6/ 17 | 7/ 17 | 7/ 17 |
Pricing
Plans as listed on each vendor's site when we last checked. Confirm before you buy.
| Attribute | Reply.io | Retell AI | Sierra |
|---|---|---|---|
| Plans | Email Volume From $49/user/mo billed yearly, or $59 monthly Email-only cold outreach. | Pay as you goOur pick About $0.07–$0.31/min Most small businesses and agencies. | EnterpriseOur pick Custom Large companies with high conversation volumes. |
MultichannelOur pick $89/user/mo billed yearly, or $99 monthly Teams running email and LinkedIn together. | Enterprise Custom High call volumes and compliance needs. | ||
Jason AI SDR From $500/mo billed yearly Teams wanting AI to run outbound end to end. | |||
| Which plan to pick | Multichannel is the best value if you use LinkedIn at all, since the add-ons on Email Volume quickly cost more. Only look at Jason AI SDR once your manual sequences are already booking meetings. | Start on pay as you go with the free credits, build one agent for your most common call and test it on your own phone. Talk to sales only once you run thousands of minutes a month. | There is one route: talk to Sierra's sales team. Agree clearly what counts as an outcome you pay for, and what setup and services cost, before you sign. |
Key features
| Attribute | Reply.io | Retell AI | Sierra |
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Pros and cons
| Attribute | Reply.io | Retell AI | Sierra |
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Who each one is for
| Attribute | Reply.io | Retell AI | Sierra |
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Questions people ask
Which is better, Reply.io, Retell AI or Sierra?
Retell AI scores highest overall in our ratings (Reply.io 3.7/5, Retell AI 4.1/5 and Sierra 3.9/5). Reply.io is best for cold email campaigns and email plus LinkedIn sequences. Retell AI is best for AI receptionist for a small business and booking appointments by phone. Sierra is best for high-volume customer service at large brands and AI phone agents that take real actions.
Which is cheaper, Reply.io, Retell AI or Sierra?
Reply.io: There's no free plan. Paid plans start at From $49/user/mo. Retell AI: There's no free plan. Paid plans start at About $0.07–$0.31/min. Sierra: Pricing isn't published; check the vendor's site for a quote.
Which is easier to use, Reply.io, Retell AI or Sierra?
Reply.io rates highest for ease of use in our scores. Small sales teams, founders and agencies running cold email and LinkedIn outreach.
How we compare
Ratings are our own, from using each tool, across ease of use, features, output quality, value for money, speed & reliability.
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