Justin,
Actually... not really. Chrono factory .357 Magnum vs. factory .38 Special ammo from a snubby, and the .357 Magnum will still have a BIG ballistic edge, even though the .357 Magnum is loaded with lots of slow-burning powder. Actually, I think somebody recently posted some chrono data of that subject on this forum...?
Of course, shooting a super-light, small revolver in a magnum caliber doesn't hold much attraction for me. But from a strictly "weight of lead at speed" point of view, there is a payoff.
As for .45 ACP... I'd look at it this way: the hollowpoint has a certain range of velocities at which it will expand reliably. Too low, nothing happens. More speed is usually more better (with some exceptions for going way beyond the bullet's design envelope). Adding 100 feet per second would mainly make the expansion more reliable in a wider range of circumstances (longer range shots, shots through barriers, and so forth).
In terms of "power" (kinetic energy, really) you are going from about 370 foot-pounds to 460 foot-pounds at the muzzle in the case of 230gr standard pressure vs. 230gr +P. 9x19 +P+ can get to around 450 ft-lbs, by the way. And for the guys keeping score, factory 10mm loads routinely get over 600 ft-lbs within SAAMI standard pressure specs.
So for .45 ACP, going to +P doesn't hold much attraction for me... the recoil is starting to feel like 10mm, but without being in the ballistic ballpark. On the other hand, maybe I'm wierd but even 9x19 in +P+ feels about the same as +P or standard loads, so from a shootability point of view having 15+1 shots with more muzzle energy than a standard .45 ACP and a flatter trajectory makes 9x19 a much more creditable proposition than people give it credit for.
So having said all that, I think that in any caliber the advent of more modern bullet designs has made the need for brute speed to get your hollowpoint working alot less pressing than it was, say, 20 years ago, when some magnum & 10mm loads weren't reliable expanders at 1,300+ feet per second.
Making a long story short(er), more speed more better if you can swing it without any problems. Otherwise, just get a modern hollowpoint load & don't worry about it.