The distinction matters practically, not just semantically.
A graphic design agency produces visual assets: logos, layouts, marketing collateral, social media graphics, packaging. The work is execution-focused. You come in with a brief, they produce the artwork. Their value is in craft, speed, and consistency of output. They're not typically in the business of telling you what to say or who to say it to.
A brand design firm starts upstream. Before any visual work begins, they work on positioning (what you stand for relative to competitors), messaging (how you talk about your value to different buyer types), and brand architecture (how your sub-brands and product lines relate to each other). The visual identity — the logo, colour system, typography, and how they all behave together — is the output of that strategic work, not the starting point.
The practical difference shows up in how the work holds up over time. A graphic design agency can give you a sharp-looking logo. But if the logo was developed without a positioning foundation, it won't have anything to communicate beyond aesthetics. A brand design firm's work communicates something specific: a category claim, a personality, a buyer expectation. That's what makes a brand defensible as competitors copy the surface-level look.
For B2B companies — especially those selling complex products to buying committees with multiple stakeholders — the brand needs to do strategic work, not just look good. That requires a brand design firm. If you already have strong positioning and messaging and just need assets produced, a graphic design agency is the more efficient and cost-effective choice.