Well, .45 +P ain't squat to the .357 magnum I often carry. No argument there ...
Carried a .357 Magnum as an issued revolver for several years. Favored either 145gr STHP for a more or less medium-powered load, and then 125gr JHP's for most other uses. Also carried a few speedloaders of the early Norma 158gr truncated nose FMJ, too. Ran about 1450fps (158gr bullet, remember), and I carried it for 'special circumstances' while working a remote, rural area. (We weren't restrcited to hollow point/cavity ammunition back then.) Had some recoil and a bit of snap to it ...
I have an early Ruger KP90DC .45, and it's been a fine pistol over the years. Had to have the slide replaced when it was brand new because of what the factory called a hardening problem. Later had to replace a few small parts here and there as the round count racked up over the years, too. Well used pistol ...
According to the factory, the current P90's use a heavier recoil spring than the earlier ones. I think it's a 13 lb spring presently versus the older 11 lb spring (which was the same spring used in the 9mm models, BTW).
Back when I was still experimenting with a lot of .45 ACP +P loads, I used some of the heavier Wolff recoil springs in my P90, and even tried a recoil spring from a P91 (talk about a stout spring). The heavier springs certainly made for a controllable level of felt recoil, but they were rather uncompromising when it came to grip firmness and locked wrist issues, depending on the loads. I started wearing a ball cap to keep the occasional errant empty case from bouncing off my forehead.
During some conversations with different folks at the Ruger plant, I was reminded that heavier recoil springs generally require heavier loads, and I might experience some erratic extraction/ejection, depending on the rating of the spring and pressure of the loads used with the different springs. Right they were ...
FWIW, I still prefer the original P90 magazines, too. I've never cared for the shorter folded-leaf type magazine followers used in the newer P90 magazines, although I can see how the small indentations in each of the magazine lips can be useful to help prevent the top rounds from being dislodged under the heavy recoil of +P loads. In my older magazines, using one manufacturer's 200gr +P load, I experienced some instances where the last live, unfired round was displaced by the recoil of the next-to-the-last round, when fired, and the last live round was ejected from the pistol, with the empty case of the fired round. Like I was later told in a Colt armorer's class, the Ruger folks told me at that time that this was likely an example of the +P load's increased recoil simply overcoming the magazine spring, and allowing the round to slip free of the magazine lips under recoil.
I also have to admit to originally (and still) being a Magnum revolver shooter. Mainly Ruger SA revolvers. Still favor them, too. While I haven't reloaded for many years, it used to be my favorite hobby which I shared with my father while growing up, and then as a young man.
I no longer carry any of my .44 Magnum revolvers as off-duty weapons ... not much time for trips into the backwoods in recent years, either ... but I still sometimes take either a Redhawk or a 629 Classic through one of our qualification courses of fire. I usually just grab whatever easy-to-reach .44 Magnum ammunition is on top in the safe or the ammunition locker ... 180gr JHP's, 240gr JHP's, 315gr JHP's or some stoutly handloaded 250gr hardcast I still have ... just to show how controllable a Magnum revolver can really be on a regular course of fire in which our folks are using 9mm, .40 S&W and .45 ACP pistols.
Not a lot of folks tend to shoot Magnum revolvers in LE circles, anymore, at least not out here. I remember using expensive store bought Magnum ammunition back when I carried a 66 and then a 686, even though remanufactured .38 Spl 158gr LSWC +P was provided at no charge for qualification. Lots of guys didn't want to qualify with Magnum ammunition, or even practice with it, for reasons of both cost and recoil, even though they typically carried it ... but I tried to wear out my last 686, running a few thousand rounds through it before ordered to turn it in for the new 9mm pistols. I missed my .357 Magnum for quite a while ...
So, aside from being a Magnum revolver guy myself ...
I never said I hadn't used .45 +P in the past, and used it by the case lot, truth be told.
Just said I didn't have any use for it ... nowadays.
Best to you MC.