Glock 23.
Sorry, I've got a bad habit of doing that......
Out of your 3 choices, I'd go with a Sig P229. Why?
1. The caliber. I like .40 S&W. It has a proven track record on the street, showing itself to be very effective in a large number of police shootings. I honestly don't think that there's anything that a .45 acp can do that a .40 can't do. The .40 is a consistent expander, and usually penetrates very well. Since the .40 is the overwhelming choice of LE agencies across the US, ammo availability will not be a problem.
A lot of R&D has gone into the .40, and it's hard to find a bad round for self defense. If you believe in light and fast, you can go with a 135 grain load at about 1375 fps/567 ft. lbs. out of a 4 inch barrel. (Double tap ammo) That is a smoking hot round, in .357 magnum territory, only with a wider bullet and bigger hollowpoint. If any round is going to expand in tissue, it's this one!
If you like slower and heavier bullets, you can go with another good Double Tap load, the 200 grain JHP at 1050 fps/490 ft. lbs. out of a 4 inch barrel. Or, all of the ammo manufacturers make the standard 180 grain load, which is the equivalent in sectional density to the standard 230 grain .45 acp load.
2. Power to weight ratio. I always look at this factor, because I carry a gun all the time, everywhere. As much as I love the heft of a good all-steel revolver or semiauto, they would get old rather quickly if I had to carry them day in and day out. The P229 is heavier than the typical polymer pistol, but it's not too bad, especially when you consider the capacity and power of the rounds. The LW operator would probably be lighter and slimmer, but at a reduced capacity. The M9 is just too big for what it is, a 15+1 9mm. If the bigwigs who decide on handguns for the military had any sense, they'd choose the Glock 19 for their 15+1 9mm. It's not like our troops don't have enough weight to carry around without lugging around the M9 hogleg. And for concealed carry? Forget it. Either the LW Operator or P229 would be a FAR better choice than an M9.
3. Accuracy. If the Operator has the P229 beat for accuracy, it can't be by much, especially at normal pistol fighting distances. Sigs are famous for their accuracy. The M9 is an accurate pistol, too, so this may be a "wash" category. Any one of the 3 will be plenty accurate for pistol combat. Match grade accuracy is not necessary for CCW.
4. Action. This one is a personal preference. You don't mention what kind of P229 you are considering, but I'd go with the DAK model. It has a consistent, smooth trigger pull with a good reset, shot after shot. No decockers or safeties to worry about, just point and shoot. I don't care for decocker models, with their long first trigger pull and subsequent light single action pull. So again, that leaves out the M9. Plus, one may forget to decock after the SEVERE stress of a gunfight for your life. No need to complicate it any further by adding extra steps to make your gun safe.
Ah, I'm gonna get beat down for this one...but I just don't care for the cocked and locked 1911 for CCW. I don't like grip safeties, I think they are pointless. I don't like having to disengage a safety before I engage a threat. I don't like the low capacity. I don't like the hammer cocked all of the time. I KNOW it's safe if handled properly, just like any pistol. I just don't like it. And yes, I know that someone's grandpa single handedly defeated the Japanese in WWII carrying only a 1911 and a bible...but I think there are much better modern designs for CCW. I own an old WWI frame Colt 1911, and I've shot a good many of them. They are SWEET shooters, and feel good in the hand. But I'll take something else for everyday CCW.
5. Reliability. Any manufacturer can put out a dud. (Even my beloved Glocks) But by and larger, pistols earn reputations based on the experience of thousands of shooters. Sigs are reliable and proven. The M9 had some early issues, but now enjoy a good reliability reputation. The Operator? Well, I don't know. That's the thing about 1911's (and another reason I carry a Glock or something else, rather than a 1911). The original JMB designed 1911 had fairly loose tolerances, and was designed to employ a 5 inch barrel, shooting 230 grain ball ammo, with a 7 round magazine. Some companies have made reliable configurations of 1911s that deviate from this standard, and some companies (including high-end maker Kimber) have failed. It's been my experience in talking to 1911 shooters that 1911 reliability is hit or miss. Some are extremely reliable. Some are not. Most are picky about magazines. Some don't like hollowpoints. If you get a good one, you are well armed. Just make sure you get a good one.
Well, enough rambling from me.....good luck in your choice!
My .