When building a services firm and determining the people resources needed to fill client-facing roles, it is usually more useful to think of the jobs that must be done (vs. the title given to the one who does them) and then be sure that an appropriate person is assigned that job where that job is important. This view is particularly useful when client situations and available skill mixes make it appropriate for more than one of the jobs to be held by the same person.

Jobs that must be done
Manage assigned resources against a plan to produce a specific outcome on time, in budget, and to specification. This function is often called project management or engagement management.

Provide oversight, guidance, and direction to several projects underway at the same time. Often called project supervision or program management.

Make sure the client properly perceives the status of all projects currently underway and that the client does what they need to do to ensure the full and intended benefits are achieved. Often called client management.

Make sure new opportunities to perform work for a client are sought out, cultivated, and closed according to a master strategy and plan. Often called account development.

Make sure that all account development and project execution activities are coordinated and properly communicated to the most senior levels of client management and internally to the firm. Often called relationship management.

Make sure time sheets are properly processed, invoices prepared and sent, files maintained, logistics properly handled, meetings scheduled, etc. Often called project or program administration. On large projects or programs, there may be multiple administration jobs. For example, all matters related to financials could be consolidated.

Summary
Take a look at each client in light of what you have committed to do and its long-term opportunity to decide which of the above roles are important to fill on each and then make sure you are clear about who will perform those functions on that account.

The truly enlightened know that everyone assigned to an engagement has at least partial responsibility for all that happens there!