1. The transaction process for both the VISA/MCI debit and credit cards are identical. A merchant must accept both and they cannot be bothered as along as they get an approval code. In fact the debit card is accepted more than credit card as a result of some rules in certain countries where local rules apply. One example is you cannot buy lottery or punt using a credit card in these countries.
2. As a general rule its always better to use your credit card rather than debit card in the event of a dispute or over fraud. The funds in a debit card are your own money or savings and if someone empties it with the use of a stolen, lost or counterfeit card, you will have to wait for the matter to be resolved especially if the sums are large.
3. A VISA/Mastercard whether debit or credit card always a better means of payment rather than Nets or Cash. The former has chargeback or resolution process and your bank will follow the route. Nets and Cash, you can kiss your money good buy if the dispute arises. Say you book a 10 day trip to China with a travel agency or an airline ticket. In the event that you paid it with VISA/ Mastercard, you will 100% get your money back if the travel firm or airline folds. No hope in hell of recovery if its Nets, Cash, or cheque. I have seen people paying for large transactions with Nets and am surprised.
4. Those who travel often will know this. Where there is no ATM fees charged for overseas withdrawal that will be recovered by the bank via higher conversion rate. It is a marketing ploy and aimed for Lau Bu and Lau Beng going on group travel for the first time.