Related על חולין 7:52

The matzah of the Samaritans is permitted, and a person fulfills his obligation on Passover [with it]. But Rabbi Eliezer forbids it because [according to him,] they are not learned in the details of the mitzvah. Rabban Shimon ben Gamaliel says, every mitzvah that the Samaritans accepted upon themselves -- they are more scrupulous in it[s observance] than a Jew.