My friend has the same bike with an 18/42 which I rode. To be honest, I didn't feel that much of a difference in take-off and acceleration.
Sure from a dead stop and on a hill maybe but these engines have so much torque, with the stock gearing I can take off as fast as I want. If I do that I have to watch the front in first (no full throttle) and second lifts the front.
As I may have mentioned, I am a relative lightweight at 70 kg.