I have been using credit card with cash back. But it seems many of my friends are “happily” using credit card with airmiles. Which one is more worth it?

If you're someone like me who seldom travel overseas, then cashback credit cards would be more suitable for you as compared with airmiles ones.

There no which is good or better argument. Different people have different priorities. I personally want cold hard cash. So I go for a cashback card. Going for a miles card helps you get into a business or first class seat for less. I guess that why many go for miles card. They want to travel in style. I on the other hand don't care. Because when I travel, the destination is what I'm aiming for. The bus journey is just that.

Which is more suitable or worth for you really depends on 1) what kind of rewards you prefer as well as 2) your valuation of an airline mile.

1. What rewards you prefer is very much a matter of personal preference. Many people I know prefer cashback cards because it is more straightforward to deal with - you spend your money as per normal and you simply get a small cashback every month. But myself personally (as well as many others) prefer airline miles cards because it allows you to redeem travel experiences you wouldnt normally pay for (e.g. claiming a first/business class flight).
2. In Singapore, an airline mile is typically valued at ~1.5-2 cents per mile, and varies based on the specific flight and cabin class that you redeem the miles for. In general, the valuation of miles vs cashback really only makes sense if you use it to redeem premium category seats (rather than economy) because the cost of these are so high if you had to pay for it with cash. If you only redeem economy flights you may be better off using cashback cards instead.

Another reason I prefer miles cards is that they typically do not have minimum spending requirements (unlike many of the better cashback cards), which for me is a great benefit because I sometimes struggled to hit the minimum monthly spending when I used cashback cards in the past.

I used to do my main expenditures on 1 card for reward points, to exchange for vouchers for electronics etc when needed. And also out of conveniences and laziness to track multiple cards.

nowadays, switching to cash back cards as every cashback goes back to you in terms of direct savings. But you have to remember the limits of each card eg some have a max cap of spending to receive cash backs on. In general to spread your spending on multiple cash back cards for maximal benefits. The card spending helps also to meet certain spending criteria for enhanced interest rates or to move up a tier eg in dsb multiplier account.

miles card.. popular for millennials as most banks offer seemingly better value on the miles given for your expenditure .. if you use it for biz class or first class redemption.. then the value per mile earned becomes lesser (if u compare with economy class, same end point, the difference is the extra comfort and experience for a higher class flight). Banks gave better ‘value” for their miles card because they know you will continue to spend on the next trip, or use the card during your travels. in most cases you will spend more than the mileage earned ... but one cannot put a value to personal happiness or experiences nonetheless..

cutting down on unnecessary spending is my ultimate aim I Guess, as you get older, you find that you don’t really need to spend big to get happiness.