EB-1A is the first-preference immigrant category for noncitizens of "extraordinary ability." 8 C.F.R. § 204.5(h)(3) sets out a two-part test administered through the Kazarian framework (Kazarian v. USCIS, 596 F.3d 1115 (9th Cir. 2010)): the petitioner first establishes initial eligibility by satisfying three of ten regulatory criteria (or by showing receipt of a one-time achievement such as a major internationally recognized award), and USCIS then conducts a discretionary final-merits determination on whether the petitioner has demonstrated extraordinary ability and sustained national or international acclaim.
EB-2 NIW is the second-preference immigrant category under INA § 203(b)(2)(A) where the petitioner has a job offer or, with the National Interest Waiver under INA § 203(b)(2)(B), where USCIS waives the job-offer and labor-certification requirements because doing so is in the national interest. The current legal standard is set out in Matter of Dhanasar, 26 I&N Dec. 884 (AAO 2016), which establishes a three-prong test: (1) the proposed endeavor has substantial merit and national importance; (2) the petitioner is well positioned to advance the proposed endeavor; and (3) on balance, it would be beneficial to the United States to waive the job-offer and labor-certification requirements.
The two petitions are different in legal theory, evidentiary focus, and adjudication posture. EB-1A is a retrospective inquiry into what the petitioner has accomplished and how the field has recognized those accomplishments. EB-2 NIW is partly retrospective (prong two looks at the petitioner's qualifications and track record) but importantly prospective (prongs one and three look at the proposed endeavor and the public interest in waiving labor certification). The same facts can support both petitions, but the framing and the supporting documents differ.
Each I-140 carries its own filing fee, and the fees are paid separately for each petition. Premium processing is available on each petition separately at the petitioner's option. Each petition is adjudicated by a separate officer at the relevant service center, and the two adjudicators do not see each other's files in the ordinary course; this means RFEs on one petition do not predict RFEs on the other, and an approval of one does not bind the other. Both petitions, if approved, generate priority dates in the relevant employment-based category (EB-1 or EB-2). The petitioner can use either approved I-140 as the basis for adjustment of status, and porting between approved I-140s is permissible under 8 C.F.R. § 245.25 in certain circumstances.