The Banshee is a light gunship optimized for swift raids on overextended and vulnerable infrastructure.
They excel at destroying Metal Extractors and other economic buildings to hamper opponents' resource gathering.
Use air Scouts to confirm raiding targets before committing to an assault, but don't scout too early and give your enemies time to prepare for air units!
Banshees are better at targeting scouts and undefended extractors than Stormbringers, but are FAR worse at truly demolishing bases. Cease building Banshees once there are no more easy targets.