This is Pierre from PTC where we are facing a similar situation : our support services organization has been using SFDC for KM for 10 years and our professional services is using multiple knowledge repositories (including sharepoint) and considering moving to SFDC.
No straight answer for you but a couple of comments
- If you plan to use SFDC knowledge, this is mainly intended for KCS practices and might not be ideal to manage the types of assets a professional services organization handles
- Do you plan to use SFDC to “distribute” your knowledge to internal/external users ? or are you going to rely on another platform (CMS, search engine…)?
- Do you have complex requirements for access control and approval workflow? if yes you might want to double-check if SFDC is matching your needs.