I'm a devout Sig fan. To me, you can't buy a finer gun. The quality control is excellent as well as the customer service. I have quite a few Sigs and have never had a problem with any of them and I think they are worth the money.
I recently picked up a P239 in .40. Excellent trigger pull, super smooth as to be expected. Fit and finish were up to par and EXTREMELY accurate for a .40, especially a small .40. First 8 shots from the gun went into a nickel-sized hole at 21 feet, 2inches at 50 feet. I'm not the greatest shot and the gun shoots as accurately as I can. Unnoticeable recoil as well.
If your wife likes it after handling and firing one, I think that's what's important. Whatever gun it is, the individual has to like how it handles, shoots, etc. As far as 9mm vs other rounds, I wouldn't worry about that. Shot placement is the most important thing to remember.
The P225 is an 8-round single stack 9mm that is slightly longer in length and height than the P239. Really fine gun. The P228 and P229 are double stack versions of the P225 and are a bit thicker in profile.
Sig now has two new finishes, Nitron and Ilaflon. Have to see how they hold up. The old K-Kote wasn't good at all and the normal bluing that Sigs have isn't the greatest. Rust isn't a problem if the gun is maintained properly but the blueing can rub off easily with some basic holster wear.
Reports of cracked frames occured on a few older P226 and P220. Those reports are gone now that Sig beefed up the guns to better handle +P ammo and such. Sig has been pretty good about addressing any problems that have occured with their products.
Check out
www.sigarms.com and
www.sigforum.com www.easterncannon.com www.Gunnery.net for more info.