You've got some good advice so far. Another thing you may want to consider is how you plan on carrying the weapon concealed on your body. The location/types of holsters, etc. can sometimes limit which pistols are suitable due to size limitations.

I have a Walther PPK that I sometimes carry in my slacks pocket with very little printing. It's only a .380 but it is very concealable. I used to carry a Glock 17, 22 and 23 in fanny packs. They're a little heavier but have more stopping power and rounds. At work, I now carry a Glock 30SF and am very impressed with it. I could carry it concealed if need be with a shirt over it in a waist band holster etc. Hopefully this helps some.