This is one of those good questions that doesn't have a single answer.

Organizational structure can be adapted to suit many purposes and many factors can be considered when determining which if any specific structure is best.  However to address your question we should look at the pros and cons of the options you outlined. 

Many organizations see Product Marketing (PMM) as owning the outbound marketing functions of the enterprise.  In many cases this closely aligns with the Marketing group's focus, and it can make great sense for PMM to be part of the greater Marketing organization. Many PMM resources are closely aligned in temperament and background to other marketeers in our organization.    In fact, in some organizations, the entire Product Management role is aligned and a part of the marketing organization.  After all, owning the market expertise responsibility is a marketing function, at it's core.  The challenge to this alignment, is the tendency to lose focus on the role of PMM in terms of bringing the market messages to the external world.  If the marketing group decides to utilize the PMM resources to primarily support the Marketing communications role, developing collateral content, lead gen programs, and the like... the gap left in the strategic role of product management is significant.

If you are fortunate enough to have a separate Product Management organization, assigning all aspects of both inbound and outbound marketing of products to that single organization may be the better choice.  This allows for leverage of the market data gathered by the Product Managers with the PMM group, as well as their participation in market sensing activities and information gathering.  The down side of this arrangement is the somewhat fractured relationship with all of the outbound marketing needs of your company.

As long as this reporting structure doesn't adversely effect the working relationship of the PMM resources and Marcom group, then this may be the preferred route.

Either way, the most important factor is that regardless of the reporting structure, all of the activities identified on the Pragmatic Framework are assigned an owner, staffed adequately, and producing the artifacts and deliverables necessary for effective marketing program support, buyer persona development, support for field training and support, and a repeatable sales process. 

I would also add that either of these alternatives is vastly better than having your PMM resources report to development or sales. So considering that, you can't make a bad choice.

Answered by Rich Nutinsky