I carry a pre-lock 342Ti AirLite Titanium (.38spl +P) in a Mika pocket holster and a 642-1 no-lock (new manufacture) Airweight Centennial in a
renegade ankle holster. I forget it's even there it's so comfortable. I can see the renegade working well with dress pants.
Loads of info at
The Snubnose Files.
Shooting +P Speer Gold Dot 135 gr through my 342 is not bad. The stock hogue rubber grips are the key and absorb alot of the explosive recoil transferred to your hand. I've read that shooting .357 through a snubnose is very painful and most don't recommend it.
The M&P 340 is the .357 / .38 spl j-frame you are referring to I believe. They come with a lock, but there may be pre-lock versions for sale on gunbroker. It's a PD I believe - personal defense - comes with the red ramp front sight and black finish. I got my pre-lock 342Ti in the stock silver finish and sent it to s&w for their PD black refinish. Much better now and they did a great job. If you didn't know, S&W has the best customer service in the business, bar none.
Read up on the s&w internal lock ( IL ) also. Smith says there is nothing wrong with the lock, but recently they started making a few revolvers without it - such as the 642-1 and 442. No difference between the 442 and 642 except for the black and silver finishes respectively. The only reason I got the 642 was it was released first - the 442 no-locks came out months later. I would prefer the black finish but I like my 642. I tried a few grips but came back to the stock s&w uncle mike's boot grips that it came with. Hard rubber, it absorbs some recoil. Tried some nice ebony wood Eagle secret service grips - very nice but no recoil absorbtion at all. They came off right away. Read the snubnose files
grip article.
If you'd like to shoot a 342Ti or 642 you are more than welcome anytime.
For carry ammo, read this:
BUG's: .380 ACP vs. .38 Sp, m4carbine.net, Industry Professional DocGKR
I'm considering switching the +P to the semi-wadcutter loads that Dr. Roberts recommends.