Ideal staff - Extrovert Or Introvert?

I recently had an intense conversation with a fellow industry veteran on the merits of hiring a gregarious, humorous employee versus hiring someone who is more introverted and quiet.  At a baseline, both employees are equally skilled at their job.

I argued that the gregarious employee should be more desirable since they enliven the work place and make it more tolerable during stressful times.  He argued that in today’s bottom line focused corporate perspective; an introverted employee is more valued.  He asserts an introverted employee works more and socializes less and is less of an HR risk. 

While I can see his logic, I argued that the introverted employee is more relevant in a science or business sector…not an entertainment sector.  However, he is convinced that our industry has now mirrored these traditional industries in their work environment – at least at the publisher level.

Thoughts?