I have a Glock 23 in 40 cal, a sig 228 in 9mm, and a sig 232 in .380 and I have carried them all concealed. My preference is the 40 for knock down power but there are many times it's just too big and bulky to carry.
The .380 gets the most carry time, small, compact, and accuate at 25 yards. Most of you will tell me a .380 is too light, but seven rounds from a .380 should stop just about anyone.
The problem with concealed carry is if the guns too big you won't carry it. The other problem is too much caliber for a small gun. Glock makes a nice sub compact 40 but you better hold on and make that first shot count because it'll take you a minute to get that little monster back under control.(Atleast for the average shooter).
But all that was completly off the subject. Go with the .40 you'll love it, my .357 hasn't seen daylight in years.