Share resource, being in a matrix organisation sharing of resource is an advantage as the project manager is able to use the specialised skill or resource required in covering their project, when one project finishes the resource can more on to other projects.
Project managers have the authority over project staff and team members, the team will need to directly report to the Pm for the length of time as they are required.
Retention of skills: Skill is retained, within a matrix organisation skills are maintained as they are transferred from one project to another.
Three disadvantages
Management of resource through PMO office, the project managers may not know who is available as and when, the project manager must ensure they are updated and kept informed of what staff is available and when, otherwise they may lose the staff and skills needed.
No one line manager, this could be a problem to team members as they could be working on numerous projects at any one time, this can have a conflict of interest between various P.m.’s as objectives and requirements may not be the same or tied up,. There may be conflict between Pms and team members to get the best out of people. Trying to please to many people at once.
I have edited your answer a bit but I still can not see three advantages and 2 disadvantages. Have another go.
No list. number your points too. Hard to mark with out structure