Interestingly, over 99% of all articles and blog posts which use a question as title will not answer that question. As if all these were click-bait by design, it looks like you cannot escape this statistically-proven fact-of-life. All such article innevitably ends up postponing the answer until you, the reader, has enough knowledge to provide his/her own answer. Therefore, the aim of the text is not to answer the question it poses, but to clarify the components that need to be answered by the reader before such an answer can be brought to light. Case in point: as the title of this post is indeed a question, you should know already that it won't provide a clear answer to the latter. Like the rest of them, our post use the question in rethorical form -- Shakespeare-style -- to discuss collateral issues as well as explain the reasons why the question it poses cannot be answered directly.
Back to the un-answerable question: SEO Agency Versus In-House Team: What's Better For You? Let's put this question in different words: Should you do SEO in-house, or outsource the entire thing to an external team? Here's what our answer would be:
To answer this question, you need to identify your needs. If you already know where you stand on the matter; if you know what your issues are and what your ideal strategy should be (assuming you have any), and finally if you know what your goals are, then more than likely you will save a lot of money by doing SEO in-house. However, there's a catch: it is almost impossible to answer any of the above unless you're already working on your SEO. So in most cases, the answer is: you'll need an agency, or at least some form of outsourced servive, to get you to the point where you can take over managing your own search engine marketing.
The author of the Forbes article mentioned above comes to the same conclusion, albeit indirectly and without providing a clear path forward. As with everything "business," the ultimate best solution is always the same: do everything you can to do everything in-house.