For credit cards, based on my experience it is not worth while to use. I tried swiping the credit card on a weekend and on a weekday. Based on my finding. Weekend rates usually very bad. Why cause banks are protecting themself due to forex fluctuations when markets open on Monday if you are using the card.
Weekdays usually banks will follow closely to the forex rates. But don’t forget that there is visa/MasterCard fees. I usually use cimb for bigger purchases in Malaysia. Otherwise prefer to use cash.