No such thing as "knockdown power" with any handgun you could shoot. 9x19, with modern expanding bullet designs have a proven track record, so don't sweat that part.
Autopistols do demanda higher level of training and familiarity. Problem is, if you take your CHL course with a revolver, that's all you can carry.

As for the RGV, there a a couple of things you can do to keep the odds on your side:
1. Don't go drinking at low end bars.
2. Don't get so drunk you cannot recognize a potential threat,
3.Don't try to smuggle any dope.

I've got several handguns that can be suitable for concealed carry. If you'd like to meet at a local range and try some out, drop me an email. (I'm partial to Greg Ferris' place, Cedar Creek).