In terms of raw power the S motor lands in the top three - it the latest iteration of Brose's venerable internal belt drive motor succeeding the excellent Brose T of 2017. Brose uses the same motor for leisure, sporty and off road - the tuning is different to suit each experience. Brose is celebrated as being the quietest and most "natural" feeling power delivery, and the S stays that course while bringing substantial improvements to motor performance.
The S series most noticeable change over the T is that high torque is delivered over a wider cadence (number of pedal rotations per minute) spectrum - it feels faster and it is, on par with the Bosch Performance series. By improving heat dissipation, the power output can be closer to 100% (vs 85% on the T) of the motor's potential without risk of the motor shutting down from overheating, and efficiency and tuning upgrades promise range improvements. There are several versions of the S motor optimized for each use - street 20mph and street 28mph, and off road for steep climbs. Specialized uses the S motor, but calls it "Turbo 1.3" and there's an app that you can tune motor performance via bluetooth on your smartphone.