This is indeed has been stated by multiple experts in ballistics. Manufacturer's aren't skimping. There is enough real ballistic data to show the differences between wounding properties of 9 and 40. 40 makes a bigger hole. 9 makes a smaller hole but before the technological changes it was doing even less. As G22Dude alluded to above, larger initial deficiencies in performance also allow for larger gains later.Source? A 180 gr HST is as improved as the 147 gr HST. I use both. Why would an ammo manufacturer skimp on applying improvements across the board?
Personally I think the 40 is a better round. For the same velocity as 9 it throws a bigger and heavier bullet that expands no worse than 9. Even though 9 closed the performance gap, I still think 40 makes a larger permanent cavity. I use 9 for four reasons. First, I don't know that theoretic advantage makes a difference in outcomes. Second, I couldn't shoot 40 worth a damn. Third is a relative cost. Fourth is that by now I am so invested in 9 that even though maybe I can shoot 40 ok now, I don't see a point.