With light taxi power set, it takes too long to accelerate to a proper taxi speed. I use a fair amount of power to get speed up to a decent figure and control with brakes from then on. You do not use differential brakes on big jets, and even differential power is not usually recommended. During taxi there is no set power- speed depends on weight, wind direction and taxiway slope. You just have to take it as it comes and keep on top of it.