People use "answering service" and "AI receptionist" like they're the same thing sold by two different vendors. They're not. They solve different problems, and buying the wrong one still costs you money.
What an answering service actually is
A traditional answering service is a room of real people answering your line under your business name. You pay per minute or per call. They write down a message and pass it along. That's the whole job. They generally can't see your calendar, so they can't book anything. They can only promise somebody will call you back. There's often a queue too, especially at night or during a rush, because the room only has so many people sitting in it.
That's not a knock on the model. For some businesses, a human voice with nothing automated anywhere near it is exactly the right purchase. Someone calling a law office about a custody matter, or a family calling about a medical concern, often deserves a person on the line, full stop, every time.
What an AI receptionist actually is
An AI receptionist answers instantly, at 2pm or 2am, with no queue, because it isn't a room of people. It's software with a phone line. Priced right, it's a flat monthly cost instead of a per-minute meter. Set up correctly, it can ask qualifying questions and book straight onto your live calendar instead of just taking a message.
It will also, occasionally, get something wrong. A caller asks something it wasn't built to handle, or the line is noisy, or the request is genuinely unusual. The honest version of this tool tells the caller plainly that they're talking to an assistant, and offers a path to a real person every time. Anything less than that is a trust problem waiting to happen.
Which one for which business
A law firm doing sensitive intake should lean toward a person, or at minimum an AI receptionist built to hand off fast and often. The cost of getting a delicate call wrong is higher than the cost of paying someone to take it.
A plumbing shop fielding forty routine calls a week, "can you come look at a water heater," "what's your rate for a clogged drain," is a different animal. Most of those calls are the same five questions in a different order. That's exactly the shape of work an AI receptionist handles well, at a flat cost, with no gap at 2am.
The rule that applies either way
Whatever you pick, write down the manual version. If the AI receptionist goes down, or the answering service is swamped, someone in your business needs to know what happens next, who checks voicemail, who calls back, and by when. Automation with no fallback is a single point of failure with a friendly voice. Build the fallback first, then automate on top of it.