[nybble41]

Visa doesn't solve the same problems as Bitcoin, so this isn't comparing apples to apples. Bitcoin isn't a centralized, credit-based payment network; it was designed as an electronic alternative to cash. (Don't forget to include the economic and social cost of global anti-counterfeiting measures necessary to maintain the USD market value in the cost of the Visa system!) Also, the reward halving schedule applies to blocks, not transactions. Any of the scaling solutions which increase the number of transactions per block (e.g. the Lightning network) will proportionally reduce the power expended per transaction.

[Tijdreiziger]

Credit-based transactions are a subset of Visa transactions. Visa Debit and V PAY were indeed designed as an electronic alternative to cash (as were MasterCard Debit and Maestro on the MasterCard side).

[nybble41]

> Visa Debit and V PAY were indeed designed as an electronic alternative to cash …

These are not alternatives to cash, they're alternatives to checks. The actual cash is held in accounts at centralized third parties (banks) who must be trusted to maintain accurate records, remain solvant, and not interfere with transactions legitimately approved by the account holders. What we see, however, is that the records are not always accurate, and banks do interfere with account holder-approved transactions, based on either their own policies or legal constraints. As for solvency… let's just hope that particular house of cards is never really put to the test.

Bitcoin, like physical cash, does not depend on trusted third parties. There are technological measures in place to guarantee accurate record-keeping, and while the sender of an "illegal" payment may be prosecuted after the fact (if they can be identified) there is little anyone can do either to prevent the payment from going through or to claw back the funds once they have been confirmed by the network.