Why European OPV requirements diverge by geography

What minimum capability should a modern European navy require from an offshore patrol vessel?

There is no universal minimum: Baltic ships need weapons for local sea control, while British or French OPVs need endurance for distant patrols.

A patrol vessel operating close to an opponent in the Baltic may need missiles and a 76 mm gun to reinforce frigates in sea-control operations. British and French ships assigned to distant patrols instead need enough endurance for long journeys and extended time away. The comparison is between deployments of less than a week in some enclosed seas and three to four weeks at sea on global duties. Those requirements affect the hull and the balance between armament and endurance. For Britain, the resulting endurance requirement helps explain why the step from an OPV to a Type 31-like frigate can be relatively small apart from the weapons fit.