Technically it should be the best woman/man for the job and often it depends on two things -

1) What profile is the startup trying to fill in? Adult supervision (read COO) at a fast growing venture backed company run by barely out of teens? You might want to poach someone like Ms. Sandberg.

2) Which sector and industry is the startup plying in? Is it enterprise software? Hiring for a VP engineering or an Engineering Manager? Hadoop or Solr specialist? Need years of experience/ deep knowledge. 20 somethings might not be the best fit. Enterprise startups like Altiscale, BitGlass, BrightFunnel, were in the news this week (funding rounds, launch) .. look at their about us pages, plenty of experience and grey hair.

Horses for courses work fairly well, inside and outside the startup world.