So you can see at the max feedrate the torque of the stepper and the torque of the servo have to be the same. Now at lower speed, the servo torque is flat, but the stepper torque is higher because of its torque curve. So, the stepper has more reserve torque at speeds below the design point. This will be true for steppers in general, not just the easy drivers mentioned before.
Servos will have a peak torque for short periods of time, which can be 3x their rated torque. So a servo can have more torque available than a stepper at any speed.