depending on what you mean by the "best".. but for me in JB, i did a lot of so called research on different brands of fuel but they were mainly based on one factor, that is knocking. so my preference below is not based on fuel economy.
I have two engines that are really sensitive to knocking, one of them so sensitive that the ignition timing is right at the borderline and if my tank is almost empty and i fill up with another brand of inferior petrol, i will hear knocking immediately as i leave the petrol station. to cut the whole story short, choice would be..
1) Petronas
2) Caltex
3) Shell
4) Mobil/Esso
note: different petrol stations of the same brand yields different outcomes!! so i tend to believe that the purity of some of them are questionable. i keep to specific branches once i've found them to be giving better quality petrol and more consistent.