If you can, try before buying. See how it shoots (from the standpoints of comfort and of minimizing shots that doe not hit the target). See how it carries. See how it conceals.
As one whose experience at the range over the years had been limited to service-size handguns and target pistols, I didn't really know what I was doing. I bought a Smith and Wesson Model 60 with target sights and a three inch barrel. Great revolver, perfect for home defense and camping and fun to shoot, but not ideal for concealment for me.
After my CCW class, I bought a Model 642 with laser sights. Really works for pocket carry. I later supplemented it with a Smith & Wesson M&P 9c with an IWB holster to get greater capacity.
However, after I learned that a practical pistol shooting course I signed up for will involve shooting about 1000 rounds plus in less than two days, I saw the need for something with reasonable capacity and more weight to reduce recoil. My hand smarts after putting a number of rounds through a light weight pistol.
After some research, I acquired a Model 1911 with a 4" barrel and an Officers' grip frame. Great shooter, and until the custom IWB holster finally came, I considered it a recreational handgun. I had never thought I would end up actually carrying a Model 1911.
But ya' know what? That's how it has turned out.
For me, it's the grip size that affects concealment the most, not the barrel length. The 3" 1911's have been known to be rather finicky. That aside, take a look at how much of the barrel is taken up by the chamber. To me, it is intuitively obvious that a little more barrel length would be desirable.
Perhaps this discussion will prove helpful:
http://thefiringline.com/forums/showthread.php?t=367567