I currently own a Sig Sauer P229 Elite in 9mm for HD. I purchased it in 9mm specifically because my wife will be learning to shoot it for HD situations. However, I'm looking for a CC gun and am leaning heavily toward the Sig P239, because of its size and the fact that I like Sigs. My real question, however, comes down to whether to get the P239 in 9mm or .40. Initially I thought I would get the .40 for a bit more punch, but I'm starting to lean toward a 9mm for the following reasons: -- 9mm ammo (such as Gold Dot) is clearly sufficient for any real threat I might encounter; -- 9mm holds more rounds; and -- 9mm ammo is cheaper and I have a ton of it (would only have to stock 9mm range ammo and 9mm stopping ammo). So, is there any compelling reason to go with the 40 instead of the 9mm?