The major difference between a quota imposed on imports and a tariff is that:
with a quota there are no revenues that flow to the government. a quota affects only producer surplus, while a tariff affects both producer and consumer surpluses. a tariff affects only producer surplus, while a quota affects both producer and consumer surpluses. a tariff affects only producer surplus, while a quota affects only consumer surplus.
Economists argue that freer trade:
helps consumers but may harm some existing producers. helps producers but may hame some consumers. helps both consumers and existing producers. harms both consumers and existing producers.