Is it better to use an app that rewards you (e.g. Grab points) or to use an app that is cheaper - spend less save more (e.g, Deliveroo)?

I would go with the latter and use gpmc to pay so that i can get the grab points as well.

In my opinion, I would opt for an app that is cheaper so as to be able to save more.

This is so as one would have to spend quite a fair bit before being able to redeem the rewards. If you're talking about Grab specifically, I would definitely go for Foodpanda/Deliveroo. It seems like the delivery price of Grab is much higher as opposed to their competitors.