I'd vote for the S&W 642 (just for the smooth hammerless design, tho we have a 637 for carry and find no problem in drawing)...for pocket use or on a belt holster the 642 is the best of the short barrels for concealed carry....Stainless steel for ease of maintenance...a good controllable caliber with a wide choice of JHP's for defensive carry...you can't go wrong....If it's fishing while carrying a side arm for snakes or whatever in the mountains of NC, or CCW carry while in the big city for dinner with my wife, or, in her case, walking the dog along the lonely country road on which we live...it's always there...for informal tin can shooting with light tgt loads, it's fun....and it fits us both...
When I bought the 637 for her, I suited it up with Crimson Trace grips for night defensive use at cross the bedroom distances...and they fit her slightly better than the issue "boot" grips provided. They were and are expensive but, like fire extinguishers, you only need to use them once, and in that case you want the best.
And here's a tie breaker...
if you EVER have a problem with the gun...S&W has in my opinion the best customer service in the industry, one phone call, answered on the 2nd ring or so it seemed...I've used them twice in the last year...once on a brand new 637 that had a cylinder lock-up problem and once on a 20+ yo M-36 with a cylinder stop worn beyond limits...in both cases, Smith sent me a shipping label, serviced the guns (and actually did some action smoothing at the same time) and I had them back in my hands in a week at no cost whatsoever...no questions asked...they were superb.
Both guns will hold to less than 2" from a Weaver Combat stance at 15 yds with any defensive ammunition that I've tried. From heavy 125 gr CCW loads, to tgt wadcutters and home-made snake shot rounds, they'll do the job.
I own a number of pistols and revolvers that are suitable for CCW, in one respect or another, but for day in day out, night carry in pocket or belt holster, or tucked in the car's glove box, one of the short barreled Smiths has been my choice for over 45 years years now. (BTW: I've four Smiths now with the much-maligned internal lock device and I've yet to have any problem with them...they remain "unlocked" for storage or carry, permanently)
JMHO, Rodfac
M-637 before we added the CT grips.
The old and much loved M-36 with adj. sights.
Some bullet pics from the 637, shot into water. Velocities were chrono'd by me.