Interesting discussion. I'm a .45 guy but do own the others...all in 1911's.
From an accuracy standpoint, ease of reloading to a match standard, and basic gunsmithing to achieve match accuracy as well as top level reliability, in my opinion and that of many many others, the .45 is the hands down winner. If you're still on the fence..why not move up to the .45 ACP, and in a 1911 type of gun as well. No double action trigger to get used to...just carry 'er cocked and locked, as she was meant to be carried.
If you're satisfied with 3+" at 25 yds from representative examples of the 9mm and .40 S&W gang, then the accuracy potential of the .45 may not appeal to you. I'm willing to concede that all three can be made to function at 99.99% reliability; but...........with the .45, it's a rare major US city that doesn't have a local "expert" 1911 .45 gunsmith that can wring every last bit of accuracy and reliability out of it. That's not true with any other caliber to my knowledge.
Handloading is another source of difference. The .45 is easy, the prescription for success easy to find...and you can do it with any brass..mixed or sorted...clean or dirty...range scrap...it's just easy to load sub 2" ammunition for the .45...and in virtually any bullet weight from 185 gr to 240 gr's. That's not true of the 9mm or .40 S&W. I've loaded 9mm ammunition since 1968 and have yet to find a consistent sub 2" load, and that's been with 3 accurized 1911 guns. If you can find one, and a gunsmith that can make that happen I'd love to hear about it. My 9's and the .40 have been to a variety of custom gunsmiths without achieving that magic sub 2" gping ability. By way of comparison, even I can probably tune the average .45 to get that standard and for less than $150 in parts outlay, it's just not that much of a challenge any more.
Same with the .40 S&W, tho my experience with this one is with a single Colt 1911A1. Never did find the magic silver bullet and believe me, I tried a bunch of combinations.
So...we're I, you...I'd give the .45 some consideration. If you balk at the magazine capacity, take another look in that sewer pipe sized muzzle, and see if you're not intimidated....100 yrs of bad guys have been! Here's some pics of my beauties. The 4 slide number is a Combat Commander with aux slides in .22 LR, 9mm, and .38 Super. The satin nickle one is the .45 ACP.
The two toned job is a factory made 1911A1 in .40 S&W; the Gold Cup Elite. The rosewood gripped 1911 Series 70 is a factory original 9mm, but with updated trigger, Wilson bushing and a cpl of hours expert gunsmithing on the slide and rails. That last sentence applies to the other two as well.
Best of luck in your quest, but remember the old bromide, "beware the gent with only one gun, generally he knows how to use it." Rodfac
Regards, my opinions alone. Rodfac