When assessing a people aggregator like SeekOut, Entelo, AmazingHiring, HireEZ, and others, or even the general-purpose Zoominfo, two points are critical:
How complete is the coverage (for your target audience)? How up-to-date is the data?
My idea is to run searches for unique names. If a combination is unique (or even unique only in a given industry and location), then searching by the full name within an aggregator will reveal:
No results? The person is not in the database. A match? Compare the rest of the data to see if the companies and titles match