Welcome to the forum. I will not be of any assistance because I too am new here and really have no experience yet. Good luck with whichever you choose. There are alot of knowledgeable people here that will be sure you make the right decision.

9mm is all you'll need for HD and it's cheaper to shoot alot at the range. I'll get flamed, but forget the .45 ACP. I have a CZ-75B in 9mm with a conversion kit to .22LR so I can shoot cheap and cheaper. It's great. I'd also consider the CZ-75 SP-01, I like it better. Just an updated version of the 75B. Sigs are great but CZ is a better value and they are so damn solid. Get the CZ and then get the SIg later on.

Bullet placement trumps ballistics, every time.
It doesn't matter what caliber you choose. What matters is that you practice with your pistol until you are quick, accurate, and effective.

Of course, anybody who tells you that the 9mm is better than the .45 ACP obviously knows nothing at all...maybe even less than nothing.
(Just kidding. )

But here's some real truth: Don't invest in night sights, light-pipe sights, a laser, or any other miracle-of-the-week or gadget, until you first have learned how to shoot effectively and well.
Once you have acquired some skill, then you will be able to discern which of the available gadgets will actually do some good for you. Until then, you will not know.

Here's another truth: Try to find a shop or range that will rent time on various pistols to you. Try as many as you can. Choose, then, with a little practical experience under your belt. And don't worry about accuracy: Any gun you try will be intrinsically more accurate than you are. Go for comfort in the hand, and recoil control.

I chose 40 S&W for my ammo across all gun platforms for consistancy. Exception is a 10mm gun.

You certainly have alot of fine guns to choose from so good luck in your selection. S&W, Springfield, Sig, Kimber...you cannot go wrong.

Definitely make sure you get to hold and at least get a feel with each pistol. Range time would be great, but that's not always applicable. I did that while shopping for my .22 and my 9. I have large hands, and I found that most CZ's just didn't fit right. Or maybe it's my long fingers (you'd think they'd be shaved down by now from my knuckles dragging on the ground when I walk, but there you go). Either way, the gun was too small for me. I found the M&P 9, with the larger grip, fit me perfectly. You will get a hundred different answers from a hundred different people. Make sure you try one on for size, is all I'm getting at.

Cannon