The two cant really be compared like that, they aim to do two different jobs.
The 45 .ACP is a rather blunt round, it will go into the target, but it wont come out the other side, it will however cause massive damege where it does penetrate.
In essence, its a low penetration-low velocity round with allot of stopping power on soft tagets, it wont travel very far though, and it will bouce off most body armour.
The 357 Mag is the opposite, its a slim long projectile with a big casing to send it on its way, meaning its a high penetration-high velocity round.
It will penetrate allot more, making it superior to the 45 .ACP against hard targets, but it wont do as much damage to soft tagets, it will however overpenatrate, meaning instead of one bleeding hole, theres two, and the target will die from loss of blood faster if youre aim was off.
So it really depends on what situation you find youreself in, against a soft target, i would want the 45 .ACP, against a hard target, i would want the 357 MAG, but thats in the real world, in INF...meh, we'll see how well they pull it off
EDIT: Damn you Zündy and youre slightly faster typing skills!