Torque over time = power. Power moves things, not torque.
The biggest difference, power wise, between steppers and servos is that the Stepper's torque drops off markedly with speed, whereas a servo does not. Also a stepper is rather severely speed limited. I just noted a document on the forum that shows a stepper loosing 75% of it's torque at high speed (high for a stepper).
Here is a comparison of the different motor types (when they are running) using Horsepower as the measure (universally understood).
HP = torque x speed / 5252
We start with equal torque stepper and servo, we'll be very conservative and say the stepper loses only half of the torqe and gets up to 1,000RPM (that would be a very good stepper)
Servo is not going to loose torque and will be running at 3,200 RPM (that would be an average servo)
Stepper 1.5625 ft-lbs * 1000 /5252 = .298HP
Servo 3.125 ft-lbs * 3200 /5252 = 1.904HP
Servo generates a bit more power. Those are the numbers.
As to the runaway issue with servos, in the case of the Gecko drive I am using, the drive provides the power to the motor, if somethign oges wrong, it simply faults and shuts down the motor. In the event the Gecko failed in some way that gave full juice to the motor, the setup can be wired in such a way that the limit switches shut down the current to the motors.
None of this means steppers are bad. It's just not a complete picture to simply compare a torque spec and draw the conclusion that the performance is anything near similar.
It is what it is. Steppers are fine for some applications, but it is inaccurate to say that they are equal to servos in performance. My rig has steppers on three axis and they do just peachy for what I need. On the other hand, even a relatively large stepper was not up to the task of running my 4th axis, so I'm messing around with my forst servo motor now.