There's definitely no one fixed answer to this, it really depends on what perks you are looking for or which area do you do most of your spending on. Here's a comparison of 4 Travel Miles Credit Cards that I personally feel are the more competitive ones in the market, and there various perks and miles earn rate.
Most travel credit cards come with complimentary travel insurance if your charge your return air tickets to the card.
Although some might say to focus your spending on just 1 credit card, I feel that no one card is perfect.
Personally I will focus more big ticket local and overseas spending and Agoda/Expedia bookings on UOB Prvi Miles MasterCard, as it gives higher miles.
*UPDATED* From 15 Jan to 31 Mar 2019, earn 10 miles per $1 spent on UOB Prvi Miles card. Book on expedia.com.sg/prvimiles.
I will make smaller purchases and airbnb bookings with DBS Altitude VISA Card, just to have a decent spending on the card and it gives 2 complimentary airport lounge access passes each year.
For AMEX Singapore Airlines Krisflyer Card, it is ideal for frequent GRAB users, as it gives 3.1 miles per $1 spent on GRAB, and there's no hard getting this extra card as there's no miles conversion transaction fee!
So, what's your take on travel miles card? Feel free to share your comments with me below!