new frameworks vs getting really good in existing /old technology

Well no one can deny that there huge number of libraries and frameworks comming up daily if all fields of programing (mobile, web, orm, mvc, ....) and mainly i find two kinds of programmers

1- Those who really do very hard work on learning and using each of the new libraries coming out in their field of interest

2- Those who are really really good in what they know in their old frameworks( can even be visual basic 6 (1998 technology) or early things like .NET Webforms, Silver light, or as old as cobol ) and they insist in keep doing everything in what they have already mastered

i understand the need for each of them in the current market (at least where i live)

Question is what are the PROs and CONs for each of them ?