El Cid's comments are accurate--both of the last two issued .40 loads were neutered mid-contract.
"9mm gets you a ~15% improvement in ammo capacity, shot splits, ammo costs, and weapon wear and tear, at a cost of ~15% decrease in terminal effects, bore diameter, and projectile weight.
The above is not accurate in my experience. 9 mm pistols tend to have more like double to triple the service life of an equivalent pistol in .40 S&W. If using a neutered .40 load, there may be no decrease in terminal effects when shifting to 9 mm.