For actuated ball valves that used to isolate vessel or any fluid services, reduced ball valve usually used for production separator, suction scrubber, glycol generator etc. While full bore actuated ball valves usually used for blow down, piggable line, production manifold, pipeline etc. Actually for blow down or any similar application, we can also use a reduced bore since the pressure drop usually isn’t significant. But usually it comes from the project specification that requires it to be full bore. It differs with piggable line that must be in form of full bore to allow the pig going through the valves at pigging activity.