It's up to your car to tell you which fuel it's gonna like best.
For example, i run Caltex Vortex 98 and BP Ultimate. The car runs like a dream on BP but its halfway across the city for me to get a tank, so it doesnt see it much.
Caltex Vortex it runs fine on, no complaints, the knock sensor never shows knock when giving it a bootfull.
Shell Optimax however has given me some cases of knock when booting... alot of people say that optimax is good to reduce knock and shit but i guess it all depends on your car, because it didnt reduce knock on mine.
So just try a fresh tank of them all and decide for yourself.