I'd compare the 9mm to a high-revving engine making power, and a .45acp to a [gasoline powered] pickup making power [no, not a diesel: that's more of a .44mag thing]. They do it differently, and both will get you from a-to-b.
9mm is like a Japanese 4 cylinder, high revving to make power, yet still economical.
The .45acp is a naturally aspirated diesel. Slow and heavy, but still has decent torque. Efficient.
.44 mag is a turbo diesel. It's like a N/A diesel, but since it's got a big turbine on it, it's faster and torquier, even with a bit extra weight.