Be Broad? Be Niche? How?

Most of the strategy I'm working on these days ends up being reduced to just a few questions:

Should my organization have a "broad" service offering (full-service approach and/or primary and specialty care integration and/or broad consumer population)? Or, should my organization be a "niche player" (discrete services focused on a discrete population)?
What are the metrics for sustainability for either market positioning choice (margin, performance requirements, price point, size/scale, vertical contracting strategy, capital reserves, etc.)?
Should we achieve our growth objectives via organic growth or a merger/acquisition/affiliation?

For many organizations, the answer . . .