Most articles on this question are written by one of the two parties. This one is on a directory of freelancers, so take the obvious discount, and then read the part where the agency wins.
Where a freelancer is genuinely better
One brain holds the whole project. Nothing is lost between the strategist and the designer and the developer, because they are the same person. On a small project this is worth more than any amount of process.
You get the person you met. Agencies pitch with their best people and staff with whoever is free. This is not a scandal, it is how a payroll works, but it does mean the person in the room at the pitch may never touch your project.
The overhead is not yours to pay. A day of agency time carries account management, new business, office, and the utilisation gap. Some of that buys you something. Some of it does not.
Where an agency is genuinely better
Continuity. A freelancer who breaks a leg is a project on hold. An agency has a bench. If your launch date has a financial consequence, that bench is not overhead, it is insurance.
Breadth at once. Five disciplines working in parallel on a tight deadline is what an agency is built for. Assembling five freelancers to do the same thing means somebody has to coordinate them, and that somebody is usually you.
Absorbing a mistake. When an agency gets something badly wrong, it has the balance sheet to fix it for free. A freelancer who works three unpaid weeks is in trouble.
Procurement. If your company cannot onboard a sole trader without a six-week vendor process, that is a real cost and it is not the freelancer’s fault.
The honest middle
A large amount of work sits between these poles: one strong independent as the lead, plus one or two more brought in for specific disciplines, with the client doing light coordination.
This is cheaper than an agency and less fragile than a single freelancer, and it is how most good small projects actually get made. It requires you to own the sequencing, which is the thing a directory sorted by availability is for.
The question that decides it
What happens if this is late?
If the answer is “we are annoyed”, hire the freelancer. If the answer is “we lose the trade show and the quarter”, buy the bench.