There are advantages and disadvantages to going in-house with a large corporate agency, as opposed to a smaller boutique agency. If you are new to SEO and you want to achieve that steep learning curve, then I would recommend applying for roles within a more specialised agency as opposed to a larger media companies.

That is not saying that large media agencies are poor at SEO and don’t have the team skills. They’re great! You can learn a lot in those places. But these teams tend to be more distracted by client servicing or preparing pitch documents, and they may not have the time to spend educating and improving your knowledge. So if you want to jump-start your career and become a real SEO whiz, then smaller agencies have a lot of advantages.

You also have the option of trying to go in-house as an SEO at a big company. These companies are, of course, laser-focused on their product, so in this case, you will quickly become a specialist. This can be good if you want to keep working in that industry, but you might prefer agency life if you aren’t sure that you want to specialise yet. Additionally, your company might not know much about digital marketing, let alone SEO, and so you will need to be a very good communicator with non-technical people.

Here is an excellent, long post from Moz about the differences between working at an agency, in-house, and freelance SEO.

There are also some interesting articles out there that are aimed at helping clients hire SEO experts. For example, this short post from Layer3 tries to educate clients about whether they should hire in-house or agency SEO. There is also a similar, longer article from SearchEngineWatch. If you read between the lines on these articles then you can learn a lot about what it might be like to work for different clients.