USDC and EURC are both Circle-issued, both EVM-native, and both EIP-3009 compatible. The choice is mostly about whose books the agent's principal balances on.
Pick USDC unless your agent operates within EU procurement constraints that prefer EUR-denominated stablecoins under MiCA.
USDC market depth is materially deeper, which matters for slippage at conversion edges and for arbitrary cross-rail payouts.