It is an age old question. My experience is that the most successful companies over the long term tend to bring in raw/young talent, develop it over the years, and promote from within.
Some companies are different and tend to look to the outside for their talent, particularly at the leadership level.
Both approaches have their pros/cons.
Some of it is what type of culture you want to build, and the type of industry/markets you serve.
Also, whether you are pursuing short term profits versus long term dominance.