What do employers prefer Specialists or generalists?

For a specific job or task you have to employee specialist, for example, some people have good technical and investigative skills they can do Root cause analysis to the extent no other HSE person can do. so companies hire them

Well its a hard one to answer but I presume - Its dependent on2 definite factors :

1. Domain of work .

2. Management commitment towards towards outcome from the domain

In current scenario most employers prefer - Jack of all trades , master of none.

Employers prefer Specialists