debit is as good as cash...comes straight out of ur account.
I would not use debit card, and I would not recommend anyone to use a debit card for small purchases... because you know - all these small things add up. In plastic you cannot see that. In cash, you HOLD the money and take responsibility - which plastic just cannot allow you to.
So I say cash money is better. Even kids SEE the money and learn responsibility. In plastic/debit they do not get to see it so they cannot learn the value yet.