Freelancers are solo practitioners (although some may operate as part of a larger collaborative or network).
They can be talented and more affordable than a design firm or big agency. They can be highly personable and passionate about your project.
Based on their experience, they may only be suited to tackle a portion of your rebrand (maybe the brand identity, but not your brand strategy or website, for example). They can have trouble sticking to deadlines (since there are only so many hours in a day). They can (sometimes) be flaky. And perhaps most importantly, because they often work in a bit of a vacuum, freelancers tend to have a single visual style that they apply to all of their client work, no matter the project context or goals. This means your “custom” branding may look eerily similar to another local brewery they worked with.