In short
Card processing typically costs a percentage plus a fixed fee per transaction, often with reserves. Crypto/stablecoin payments usually cost a platform commission plus small network (gas) fees. Card-to-stablecoin gateways combine both, so weigh total cost and settlement control.
What makes up each fee
Card fees bundle interchange, scheme fees, and the processor's margin, and can include chargeback and reserve costs. Crypto payment fees are usually a platform commission plus on-chain gas (tiny on Polygon/BSC). With Bitoshi the platform commission starts at 0.90% and there are no rolling reserves.
Part of our guide to how to accept crypto payments.