A pair of Republican senators are marketing their bill to legalize the beneficiaries of an executive amnesty program as a tougher alternative to a competing Democratic proposal, but immigration skeptics say the bills are hardly different in substance. Known as the “Succeed Act,” the GOP bill would give legal status to younger illegal immigrants covered under the now-cancelled Deferred Action for Childhood Arrivals (DACA) program. It requires applicants to meet strict education or work requirements to be eligible for a green card and lays out a 15-year path to citizenship — 10 years in a conditional status period and then...