Answer:
Similarities:
The organization were founded around the same year: SDS or Students for a Democratic society was founded in 1959. Young Americans for Freedom (YAF) was founded in 1960.
Both organizations represent college students opinion in the USA towards different government policies.
Differences:
Students for Democratic Society (SDS) had its origins in the student branch of the League for Industrial Democracy, a social democratic educational organization whereas Young Americans for Freedom (YAF) is a conservative youth activism founded as a coalition between traditional conservatives and libertarians on American college campuses.
The purposes of creation are different: SDF was operating under the principles of the “Port Huron Statement,” a manifesto written by Tom Hayden and Haber and issued in 1962, the organization grew slowly until the escalation of U.S. involvement in Vietnam (1965) wheresas the purposes of YAF are to support public policies conpatible with the Sharon Statement, which was adopted by young conservatives at a gathering at the home of William F. Buckley in Sharon, Connecticut, on September 11, 1960.