My debit card is issued by Visa, but MasterCard AFAIK doesn't differ in that case.
I can use it to pay in shops, online, to reserve place in hotel etc.
I manage to constantly have enough money on my bank account, as I would manage to pay credit card on time, the only difference is, that my 'card limit' is as high as I need it to be - by managing money flow.
I don't consider possibility of 'free credit' and profiting from interests since interests are currently (EU) unreasonably low (under 1 percent) and that percent I could get on the lump sum of purchases doesn't matter for me. AFAIK you don't build credit history in EU by purchasing bananas as well, so if I were to take mortgage, only my previous mortgage would count.
Under that circumstances, would I ever need credit card? Can I approach situation, where MasterCard/Visa debit card would not be accepted and MasterCard/Visa credit card would? Can a merchant know if I give him number of debit or credit card, accepting only 2nd one?