They are described with the same two words — extraordinary ability — and the criteria lists look almost identical. That resemblance is real, and it is also the reason people make a planning error that costs years.
The honest way to compare them is not criterion by criterion. It is by asking three questions: who files, what the evidence has to prove, and what you have at the end.
Who files
The O-1A is filed by a U.S. employer or an agent. The beneficiary cannot be the petitioner — that is not a formality, it is the structure of the category. A company you founded can petition for you if it is genuinely capable of controlling the terms of the work, which is a question about the company, not about your shareholding.
The EB-1A is a self-petition. Nobody files it for you, no job offer is required, and no company needs to exist. For someone with a strong record and no sponsor willing to carry a petition, that difference is the whole decision.
What the evidence has to prove
Both ask for three of a list — eight items in 8 CFR 214.2(o)(3)(iii), ten in 8 CFR 204.5(h)(3). The lists overlap heavily: awards, membership, published material about you, judging, original contributions, authorship, high remuneration.
What differs is the standard the three have to carry.
The EB-1A definition in 8 CFR 204.5(h)(2) asks for a level of expertise indicating that the person is one of that small percentage who have risen to the very top of the field. And meeting three criteria does not end the analysis: USCIS then steps back and asks whether the evidence as a whole shows sustained national or international acclaim. That second step is the final merits determination, and it is where records that counted to three fall apart.
The O-1A is a temporary category for coming to work in the area of extraordinary ability. It is demanding, and it is not the same question.
What you have at the end
An approved O-1A gives you status, for an initial period of up to three years, extendable in one-year increments to continue the same work. It is renewable but it is not permanence: it depends on a petitioner continuing to exist and continuing to want you.
An approved EB-1A gives you a green card. No employer, no renewal, no dependency.
The mistake, stated plainly
An approved O-1A is routinely read as a rehearsal that was passed. It is not. The two share evidence and do not share a standard, and a file that satisfied an officer for temporary work can be read very differently when the same facts are measured against a permanent one.
What follows from that is practical: if the EB-1A is the destination, the evidence should be built to the permanent standard from the start, even when the O-1A is what gets filed first. Building to the lower bar and upgrading later means doing the hard part twice, and doing it under time pressure the second time.
The reverse case matters too. Plenty of people file an O-1A they do not need, because an employer offered to, when their record would have carried a self-petition and saved them the dependency entirely. That is a question worth answering before the first filing, not after the third extension.
Where to look next
The catalogue pages for O-1A and EB-1A set out the fiche for each — who petitions, the standard, the timeline and what is payable. If what you actually want to know is which one your own record supports, that is what the free assessment reads, against the ten criteria rather than against a general impression.