The Firearms Blog says they aren’t really equivalent. Certainly that’s the case with the full-house round only available to the military, but the civilian rounds are considerably neutered. The SS196SR reports a muzzle velocity of 1650fps fired from a Five-Seven. This round is discontinued though, and has been replaced by the SS197SR round, which 1750fps.
Still, the point they aren’t really equivalent is a good one. That’s still 272 ft/lbs as opposed to 139 ft/lbs for the .22 Magnum. But I have seen other 5.7mm loadings that have even lower muzzle velocity than the SS197SR round, but there are also loadings of 5.7mm that are hotter too. In terms of overall capability, I think Steve is correct to point out the 5.7x28mm outperforms the .22 Magnum. It’s only in considerably neutered loadings does the 5.7x28mm come down close to the .22 WMR.