Usage examples for gainer:

• Sure the Doctor err'd in his Vocation: Had he quitted all serious Matters, and dedicated himself wholly to Drollery and Romance, with two or three Years under Hudibras, he might have been a Master in that Faculty; the Stage might have been a Gainer by it, and the Church of England would have been no Loser. "A Discourse Concerning Ridicule and Irony in Writing (1729)" – Anthony Collins

• Auburn, the loveliest city of the plain, the loser; but Ithaca, the Forest City, the gainer "History of the Dewitt guard, company A, 50th regiment National guard, state of New York" – Unknown