This is a debate I keep having internally with my team and I want to hear from people who have worked with both.
The argument for a generalist is straightforward. A strong designer understands visual communication principles that apply across contexts. Good typography, strong composition, effective use of color and contrast. Those fundamentals do not change whether you are designing a billboard, a Meta ad, a trade show banner, or a product one pager.
The argument for a specialist is that advertising design operates under constraints that other design work does not. You have two seconds of attention in a competitive feed. You are designing for a thumbstop moment, not a considered viewing experience. The visual hierarchy has to communicate the value proposition before the brain has consciously engaged with the content. That is a very specific craft and it is not the same skill as making a beautiful brand identity or an elegant infographic.
In my experience the designers who are genuinely excellent at promotional design and commercial creative tend to think about their work differently from designers who are excellent at brand or editorial work. They are optimizing for a behavioral outcome rather than an aesthetic experience. Who have worked with designers specifically on advertising creative, did you find that specialization in promotional and commercial design made a measurable difference to your campaign performance? And how do you evaluate whether a design partner has that specific skill set before you commit?