Okay folks, sophomore engineering.......

The newer hollow spindles are stiffer in torsion, meaning there is less angular wind up as you pedal. However, this wind up is extremely small, and probably won't be felt by the average, or even above average rider. The work energy needed to wind up the shaft is returned to the system at the bottom of the pedal stroke.

Lateral stiffness is a function of the frame, not the spindle diameter or the placement of the bearings. A frame is flexed laterally due to a sideways torque. A crank's "Q" factor will have an effect on this. As before, the energy is returned to the system.

Either way, essentially no energy is lost, so it doesn't make any difference in performance.

There is no need to obsess with "stiffness" in your bottom bracket. Those that do probably obsess with stiffness in other areas.

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