Base and Arbitrum are both production-grade EVM L2s with native USDC. Current CDP documentation lists both mainnets for x402 v2, so the useful decision is buyer-wallet fit, treasury policy, facilitator configuration, and the endpoint's live payment contract.
The free scorecard organizes the constraints you already know. It does not claim that either network is universally better or replace a live HTTP 402 check.
No wallet, API key, or settlement. Ontario returns a point-in-time report ID and shows the next step only if the evidence warrants it.
Attach the public report to one email. Ontario returns go, fix-first, compare, or not-a-fit. No charge exists until the $99 memo scope and deliverables are confirmed.
Protocol support checked against official CDP documentation. Ontario does not guarantee safety, catalog placement, ranking, settlement, traffic, or revenue.
Neither rail wins by protocol support alone. Choose the network that matches the buyer wallets, treasury policy, facilitator configuration, and operational evidence you can support, then validate the live HTTP 402 contract. A rail choice does not prove that an endpoint is ready or worth paying for.
Base or Arbitrum can be the right rail and the endpoint can still expose a stale manifest, malformed HTTP 402 challenge, wrong price, or unsupported asset. Run a free Ontario preflight before authorizing a payment, then keep the report ID with the agent's decision record.
Ontario provides observable readiness evidence, not a safety, ranking, settlement, or revenue guarantee.
A network comparison is useful, but the decision depends on the endpoint's live 402 challenge. The preflight form is above so you can test it before reading the longer comparison. Use the links here to inspect the report methodology or request a scoped review.
The check is point-in-time evidence. It never signs a payment or buys a real-world good.
An x402 service should declare its supported network and default clearly so an agent can compare the payment challenge with its policy. Verify the endpoint's live 402 response, accepted asset, price, facilitator metadata, and report freshness before authorizing spend.