That's the dumbest that I've ever heard. Wider bullets will always do more damage regardless of any advancement in bullet technology. The width disparity only increases with expansion because of cross sectional density. Modern hollow points expand more consistently and with greater weight retention than older designs. They aren't somehow deadlier because of their construction. A bullet needs to be as wide as possible with more than adequate penetration. 9mm fails on both criteria and can only realistically be considered marginal for self defense.
Damage is negligable upon the round. Please refer to these charts as reference.
45 Cal acp
45 ACP Stopping Power
9mm (roughly 30 cal)
9 mm Stopping Power
Best performing 45 acp round was: Remington 185 gr GS (Golden Saber) with a 69 cal expansion and 12.4" of penetration.
Best performing 9mm round was: Federal 124 gr HS (Hydra Shok) with a 67 cal expansion and 14.5" of penetration.
Looks like the 9mm round got the expansion and the penetration.