Pros
Contagious passion for their client. Always enjoy working with them because they are open to new ideas and lean on the expertise of the people they bring into a project. They have their own creative goals and communicate them but they always think through choices when presented with new suggestions. Very detailed oriented ramping up for a production which makes things easier on the day of. That being said, they are also flexible to new approaches on-set and help to create and support a fun studio environment which helps the actors, crew, and thus the product immensely.
Cons
I can't think of any cons. The demands of advertising, production, and anything that hovers over the creative arena are infamous. Its a great career to pursue and not for the faint of heart.