I live in South Texas myself, and I won't carry anything unless it's either stainless, alloy, or finished in a protective finish such as satin nickel.
When carrying IWB in the summer, my carry pistol is always wet with sweat when I take it off at the end of the day.
As far as caliber, revolver or auto, there are too many personal decisions you have to make that others can't help you with.
How "deep" do you want to conceal?
How fast do you demand that you be able to access the weapon if needed?
What's your personal philosophy on "stopping power"?
There's lots more questions you need to answer for yourself, and what's likely going to happen is that you end up with more than one carry piece for different situations.
My primary carry piece is a stainless Colt Commander in a VM2 holster (IWB), but in the winter when I can wear a jacket, I'll carry it OWB in an Axiom holster.
In really hot weather, it depends on how I dress, but I vary my choices between a German made PPK .380 (plated in satin nickel), a 642, and in about a week, my Rohrbaugh (micro 9mm) will be here.
I don't think there's just one answer for carry for all of the time, but you will probably end up with a choice for carry that works for you most of the time and that's what you're looking for your first choice to be.
The best that anyone else might be able to suggest is a few pistols where "you can't go wrong", and some of those pistols might be along the line of a J-frame Smith such as the 642, or the more concealable P3AT Kel-Tec that has a "decent" reputation for reliability if you want an autoloader.
If you are comfortable carrying more mass, there's always the small frame .45's like the Colt Defender and other's similar to it made by Kimber etc., and staying in the 1911 category, you might like the Springfield EMP which is one of my favorites (but it's too darn pretty to add wear to it by carrying it excessively). The EMP is a single stack 9mm that is very easily hidden in the right holster. (Probably more relevant advice you should consider is that the holster you choose may be as, or more, important than the pistol you choose.)
Be careful with choosing one of the high-cap polymers such as the Glocks and Springfield XD's. While they all have great reputations for reliability, they are so darn FAT that they do not conceal as easily as would a Commander size pistol that's much thinner.
I have an XD9Sub-Compact, and while it's also one of my highly favored pistols, I find that I'm only comfortable wearing it if I can wear it under a really thick sweater or jacket in the winter months.
So the only thing I will advise without reservation is to stay with stainless or plated or polymers in order to avoid corrosion and rust.
All the rest of what you should consider; you're on your own.