The immediate or deferred debit thingy sounds like a useful thing to have. The Carte Electron sounds more like UK Switch cards (although I'm not sure whether those still exist - were they taken over by Maestro?). I always assumed that my debit card would take the money from my account immediately, but it takes just as long to clear as a cheque would.French Visa cards have as an option débit immédiat or débit différé. In the first case it works like a debit card in that the cash comes out of the account ASAP and in the second you get till the end of the month, though I guess their are other options.
There is also a Carte Electron which really is a debit card, linked directly into the banks, and the cash comes out out of your account immediately.