I used to carry an older stainless 649 Bodyguard at work as a secondary weapon (older .38 version).
After I bought my first 642-1 I decided the little Centennial Airweight was the better way to go. Of course, I'm a long time revolver shooter (who likes Magnum revolvers), so the lightweight DAO snub was a handy gun for me.
The 442 is nice for having a dark, non-reflective finish, if that interests you, but the carbon steel barrel, cylinder & yoke aren't going to resist oxidation like the stainless steel used in the 642. Your choice. How much daily care & attention are you willing to invest?
I find the Airlite snubs (Scandium frames & titanium cylinders) to be really light to carry, but harder recoiling.
My favorite of them all is the M&P 340 Centennial. It's chambered in Magnum, but I mostly use & carry +P. (They make a version only chambered in .38 +P, originally produced for LAPD use.) It falls between the Airlites & Airweights in weight.
The thing I like best about the M&P 340 is the XS front night sight. Fast & easy to pick up for aimed fire. The Scandium frame makes it expensive, though.
All things considered, the 642 is probably the best deal going, as S&W offers them for great prices through their LE distributors (and some S&W dealers seem willing to offer them for decent prices). The 642 is still their best selling revolver, last I heard. The 442 is a close second.
Where & how to carry it? Depends on your needs. Talk to your firearms training unit or instructor about some methods. Almost all methods have their proponents and detractors, with advantages & disadvantages to carefully consider.
I've been attending some updated training this year. The effective & successful use of the little 5-shot snubs have continued to grow. In one class I attended, the instructor (retired LASD) was able to relate a number of instances where cops were able to fall back on their 5-shot backup snubs to successfully deal with 1, 2 & even 3 attackers.
Nothing "wrong" with some of the better .380's, either.