If you are able to split across many different cards, I would suggest:
- Amaze + Citi Rewards (1k SGD, about 0.5cpm ignoring opportunity cost)
- Chocolate Visa (1k SGD, no cost only opp cost)
- Maribank (1.5k, no miles 1.5% cashback)
- Trust Credit Card (no cap, no miles 1% cashback)
If you are limited to 3 cards (which is typical), I would actually suggest to go like this in this order:
- Chocolate Visa (1k SGD)
- Maribank (1.5k SGD, 1.5% cashback)
- Trust Credit Card (no cap, 1%)
Reason being your first 3 cards are limited by a spending cap, so you have to rely on Trust CC to pay for at least 4k (if you drop Maribank) or 3.5k (if you drop Amaze or Chocolate). Choosing which of the 3 cards to drop is easy assuming your miles valuation is 1.5cpm:
- If the choice is between Chocolate and Amaze, Chocolate wins because Chocolate cost 0cpm while Amaze costs 0.5cpm (ignoring the same opportunity cost)
- If you drop Maribank, the cost per mile of Chocolate and Amaze are 1.5cpm and 2cpm respectively if you include opportunity cost (because you are giving up the 1.5% cashback). That means that Maribank is always a better choice than Amaze.
- Since Maribank > Amaze and Chocolate > Amaze, that is why if you are only allowed to pay using 3 cards, you should drop Amaze.
The only time Amaze > Maribank is if your miles valuation is more than 2cpm, which is higher than average and what most bloggers recommend. And if your miles valuation is below 1cpm, just go cashback entirely (not even chocolate visa)