credit card - most issuers charge 3% currency conversion fee

Ah San, you are rich enough to not care about the additional charges. :-)

Seriously, I use Credit Cards when making purchases aboard that have potential of dispute (merchandises not up to promise, for example) because Card provides consumer protection. So I am willing to pay the 3% currency conversion fee.

Otherwise I use ATM cards to get local currencies and use cash for transportation, meals, that kind of thing.

The only exception is for Canada - where my Citi dividend card would rebate 5% on gasoline and grocery purchases - so after paying 3% fee, I still get 2% back - that would be the only case I use Card for those types and only in Canada.