How else is executive search different from other types of third party staffing services?
The key difference is that executive search seeks to work in partnership with the client. This is the only way to assure high quality results.
It also means that clients need to be prepared to work with the executive recruiter as an equal or peer during the recruiting process, rather than as an agent that passively follows orders given by the client.
For this reason true executive recruiters specializing in middle to upper level assignments tend to focus on retained searches.
Advertised searches and contingency assignments reflect the vested interests of job seekers looking for new opportunities and recruiters "pushing bodies" (respectively).
These conflicting goals take away from the main goal: to locate the best quality human talent available to solve a particular client's strategic staffing need.
This may mean attracting talent away from companies where they are currently (and happily) employed.