SSN flexibility versus SSGN missile capacity

What are the practical differences between an SSN and an SSGN?

An SSGN carries many more missiles and focuses on strike; an SSN with missiles is a more flexible but compromised multi-role solution.

The comparison is about mission compromise. A converted or purpose-built SSGN can carry many missiles, approach quietly, launch, and withdraw while concentrating on the strike task. An SSN with cruise missiles must still hunt enemy submarines, either carrying relatively few weapons or accepting a large inserted section. That extra length and altered form may impose acoustic penalties, so a wealthy navy gains by keeping dedicated strike boats and hunter-killers rather than accepting one seventy-percent solution.