Complicated subject and I'm still learning.
Torque = Bench press how much can you press
Horsepower = How many reps can you do
300 lbs x 1 rep lets call it 300 hp
30 lbs x 10 reps 300 hp
From a physics standpoint it doesn't matter if you move the weight all at once or over time, the same work was performed.
If you look at the torque curve of a engine produced by a dyno the torque sharply increases to a point and then tapers off. On a diesel engine this peak comes early, on a gas engine much later. The peak measures the point in the rpm range the engine is operating most efficiently, getting the most power per stroke. On a motorcycle (or car) this is the point you will get you maximum acceleration without changing gears. On the Versys it is about 7,200 rpm.
Think of the gearshift as a torque multiplication selector. When you are in 1st you are multiplying the torque to the rear wheel by 2.438 times. The trick lies in finding the spot in the torque produced to the rear wheel is less in first multiplied by 2.438 than it is in second multiplied by 1.714. There is no point like that so you are limited by the redline, rev limiter at around 10,500. You shift to 2nd at 10,500 and your rpms drop to 7,400.
Now you are comparing the torque produced to the rear wheel multiplied by 1.714 (2nd) to the torque produced to the rear wheel multiplied by 1.333 (3rd). The spot where the torque to the rear wheel in 3rd exceeds the torque to the rear wheel in 2nd comes at about 9,500 rpm, at around 9,200 in 3rd, around 9,000 in 4th.
Have I put you to sleep?