Hmmm, your explanation of how Transferwise works is exactly how I always thought that Revolut works as well. When I saw that Transferwise is offering some kind of card I started thinking that they are the same thing.
Maybe Revolut works the same way, I don't know. There's no third party with Revolut though - it's supposed to be mainly used as a personal bank account/credit card when travelling abroad or making international payments, whereas Transferwise involves transferring money to a separate company who then transfer the money on your behalf.
But the big question as asked by Larrabee, which is cheaper? I'm trying to avoid spending hours running the numbers.
Going by today's exchange rate, if I were to exchange £15 GBP unto USD in my Revolut account (which is about all I have in the account at the moment), it would give me $18.56.
If I were to transfer £15 to my US account through Transferwise, after fees, I would get $16.78 (paying by debit card) or $16.82 (by bank transfer).
So, looks like Revolut has the better rate.