That's correct.With payment processing you mean wire transfers / bank transfers not card processing ?
For reliable card processing in USD we indeed use local Panama Banks as they have a quite high risk appetite and settle instant to your Business Bank Account in Panama. Fees can be negotiated.
However for SWIFT Transfers we prefer Hong Kong and UAE as Banking Jurisdiction as it's more streamlined and cheaper to process Wire Transfers.
Panama Banks tend to take 3-5 Working Days for a USD SWIFT Transfer while charging on outgoing Transfers 50-100$ and incoming Transfers 30-50$ so you can end up paying 1000$ per Month just in Banking Fees for 10 Transactions.
Hence we pick the most streamlined and affordable solution available depending on our clients individual situation.