Sketch two axes that intersect in the lower left. The horizontal axis describes work sent out to law firms on a scale of legally simple to complex (well-known law applied to straightforward facts in one state or country on up to multiple areas of law that intersect, sophisticated structures or issues, several jurisdictions) while the vertical axis is a scale of scope (single lawyer and paralegal can handle over several weeks on up to phalanxes of associates and partners and support staff needed for years).
The lower left quadrant (not complicated and modest effort) is standard fare for local law firms; the lower right quadrant – more complex but moderate scope, the stuff regional firms handle well. The upper left quadrant, where complexity is much greater but the scope is still manageable falls to boutiques, while the upper right – broad of scope and sophisticated in demands — would be the realm of the national or global firm.
When hammering out a legal issue, the trick for a law department is to match the firm to the forge.