9mm 124 gr +P Golden Saber - 1180fps for 384 foot pounds
.38 125 gr +P Golden Saber - 975fps for 264 foot pounds
Thus, the 9mm is 31% more powerful than the .38. I don't think a difference of almost a third is insignificant or even really similar, at least on paper. Maybe gelatin would tell a different tale, but I suspect 9mm will substantially outperform .38 there as well.