I picked 40 because I wanted a bit more oomph than a 9 if I needed it and wanted more rounds than a 45. Again if I needed it in a self defense situation. Mammels on adrenaline can do some whacky things.
The 40 sends more energy to target than the 9 (See specs on the ammo posted above this from "Constantine", 180 grains over 1000fps in a 40!!). And it's easier to handle (gun control) than the 45 for most folks. You should get with some of your buddies that have pistols and shoot some of each. Or find a range where you can check out different ones and try them. My son had a glock in 9 and sold it, then switched to another glock in 40.
I bought a Taurus Millenium Pro and loved it. It's a shorty for concelament and is a bit "snappy" in 40, as some have mentioned.
I liked the Taurus so much that I bought another Millenium 24/7 Tactical and liked it even more. The tactical is a full size, 5 incher. That ended the snappiness and improved my scores at USPSA but it is a bit large for concealed carry. I shoot USPSA to practice and become more proficient, not so much to compete (except with myself). And it's a ton of fun too.
So yea, if comparing calibers make sure your going apples to apples. Don't compare a full sized to a compact in different calibers.
I know of a few stories of people who bought Taurus's and hated them but mine worked flawlessly.
I believe most state troopers use the 40 or the 357sig. That's gotta mean something.