A subject-matter expert is a person who is an authority in a particular area or topic. In the consulting world there are firms that specialize in a particular industry or vertical as well as firms that consult in business practice on a broader basis. Those types of firms are also still capable of drilling down to the specific needs of an organization because of certain members on their team, or because organizations that they are aligned with, in which they outsource for specific subject matter expertise..

As an example there are consulting firms that deal specifically for instance  in the healthcare space and that is all they do, which would lead you to believe that they would be the best subject matter experts in most areas of the healthcare space. In contrast a competing firm in the Healthcare space may also deal in multiple verticals such as Finance and Banking, Distribution, Transportation, Media, Education as well as Healthcare. A general consulting firm and that aligns themselves with experts that are more specific to the drilled down needs of a Healthcare organization may be better suited to provide solutions than the firm the specializes in just Healthcare. Additionally the firm that deals in multiple industries may be more well rounded from a business perspective and quite possibly could use knowledge gained from experiences in other verticals that would also be a best practice solution in the industry they are working in.

There really is no answer to this question as it depends on the issues facing an organization and their ability to determine which consulting firm best fits those needs. The reasoning behind raising this point is that there are subject matter experts that may be more qualified outside of a consulting firm to address certain needs that their staff is not a qualified to address. A good consulting firm will utilize these experts when the level of expertise is beyond their capabilities. Delivering the results needed to solve the issues facing the client is all that really matters in the end.