Hi everyone was just noticed this thread recently and thought I share a recent experience with you guys.

Recently I was unfortunate enough to experience a theft of my credit card and the card was used before I realized it, hence I was not able to block it. It was a financially painfull experience but out of this experience, I got to know some information which will hopefully be a part of your consideration when choosing your credit cards.

In a nutshell, I lost 2 cards, one belonging to HSBC, and one belonging to Citibank. HSBC detected the usage of my card and called up to ask if I had used my card to transact a large sum. I mentioned no and thanks to their quick action, they called up the merchant and they manage to stop the transaction. That saved me a large sum of money.

On the other hand, my experience with Citibank was totally diffrent. When Citibank called me up to ask if I had used my card, I replied no. I asked them to immediately call the merchant and cancel the transaction. They refused and gave all sorts of excuses like

- We don't know where's the merchant
- We don't know the number
- The guy may have left by now

And instead of helping me out, they just insisted on  asking for my information as to where to send my new replacement card to. It was a pretty fustrating experience and as a result, I now have a dispute with them.

As part of my dispute, I have highlighted to them that I told the person who called me on that day, to call the merchant and try to cancel it, but the person flat out refused to do so without even trying. They have refused to look at this point and have made me fully liable for it. I recently met up with Citibank's fraud department manager and I picked up the following during our conversation:

- Diffrent banks have diffrent policies when treating these kind of cases (Notes: this is the answer given to me constantly whenever I asked why no attempt to call was made. I hazard that it implies that diffrent banks may have diffrent processes when hit with these cases and may include whether or not they will try to call)
- She claimed that the merchant may sue them if they called the merchant to cancel the transaction!
Summary
After the incident, I asked a number of banks, if it is possible to block any transaction above a set limit (e.g RM200). All banks responded that they can only call the card holder if they detected a transaction more than  RM200. They CANNOT block the authorization of the transaction. Hence, if your card is stolen, and someone used it to transact a certain amount and the bank did not or is not able to stop the transaction, you will very likely be held liable for that amount (especially if it is a large amount and depending on the situation and circumstance of how you lost it etc) and you will have to dispute it with the bank or go through the FMB.

From the point above, the varying ways and processes in which a bank handles the situation at the moment of fraud, will really make a diffrence and should be a very important consideration point when choosing a credit card issuer. Clearly HSBC was better in handling the situation, at least they made an attempt to call and block the transaction while Citibank did not even try, resulting in my money being lost.
Dear friends, I'm not writing this as a person disputing a transaction with Citibank. I'm writing this because I feel that discrepencies in handling of these cases between banks, makes a huge diffrence for us card holders. It may seem diffrent banks have diffrent ways of handling these cases and may include whether they will call the merchant or not (especially if the merchant is tied with another merchant bank). I hope none of you have to go through what I went through. But when push comes to shove, it's good to know whether your bank will help you, or just keep quiet and let your money slip away. The feeling of knowing, at that moment of time that your card had been used, and the bank totally refuses to help you, is a really depressing feeling. Hope you choose wisely on the bank your credit card is tied to, not just by looking at the rewards or benefits, but at the security and how the bank handles or protects it's card holders during moments of crisis.
I'd love to hear your opinions as well as a card member of both of these banks, i'm sure there are differing experiences. I could not include all the info here, so if you guys need additional info, I'd be glad to oblige. 
Edited: Corrected some points and statements