This is strictly anecdotal as I am by no means a materials expert, but having a large stock of steel spokes that was given to me, I use them on cheap builds for kids bikes. I can tell you that it takes considerably more force to shear them in my spoke cutter than stainless spokes of the same gauge.
I am open to being corrected on this, but my experience leads me to believe the steel is stronger in shear strength if not tensile strength.