F In my experience, if its an old terminal the debit works exactly as a creditcard (I even had to put down my signature in some places), for others I would be asked on the terminal whether my card was Debit or Credit. Both choices would work (I tried), its just another route to the same process I guess..
I can only see a human refusing the Debit card as it reads Debit on the card, but it could just be me. Bunq imo is really vague on the differences between these two cards, as for the Debit card they also always said 'it also works for hotels and car rentals but they will hold a deposit on your account'. But usually when the differences are really vague, there are no real differences..? :)