I think what ship was getting at was lack of overpenatration, which shouldn't be equated to less stopping power. As an example- I've heard entry teams use AR carbines as opposed to 9mm subguns because the former is both more lethal AND less likely to go through the bad guy.
As for your concern to the 5.7s lethality:
To be blunt to there hasn't been enough people shot with the 5.7 to really judge.
Most of the people who have been shot with this round have gotten it full auto from SWAT and special police carrying the P90. In two such instances that have been publicized the bad guys were killed instantly and the wounds were reportedly 'impressive'.
I read an account of an officer disabling a bad guy with one shot from his USG, he shot the guy in his hip region.
From all the material I have seen shoot with the 5.7 I think it is probably more lethal than the 9mm. It tends the yaw or fragment (depending on type) after impact, and in both cases leaves a cavity that you could fit some kind of fruit in.
I don't really believe in 'knock down' but round- for- round .45 ACP is defiantly going to do more damage on an unarmored target.
The thing is that 5.7 has such low recoil that you can likely put twice the rounds on target in a given amount of time. In two seconds I can draw and put 4 5.7 rounds on target, with my .45 I've never gotten 3.
You can see my point.