So that's why there is a fuel drain on each wing tank of my Archer ???? I should put that on my checklist... ;-)
I try to stick with one brand all the time, Mobil in my case, when ever possible.
While the fuel comes from the same reffinery, each brand has it's own additives. And since the ECU is basically finetuning the engine all the time, I feel that making the fuel a more consistent factor, there is less changing of the settings required which should result in a minor improvement of performace/mileage.