Of course engine oil more important. To me, coolant doesn't need to be branded as long as it does the job. But there are common mistakes that people do, like
- topping up with pipe water
- mixing different types of coolant
- not using the correct mixture ratio
- not changing at recommended intervals
- flushing with pipe water and top up with concentrated coolant.

Personally I use Toyota premixed 50/50 coolant and change every 40,000km.