qkrthnu,
I recently purchased a 340PD for the specific purpose of pocket carry. The first thing I shot out of it was 158 gr. Fiocchi FMJ, which (at 960 fps) is as hot as any "+P" out there. And yes, it slapped the ____ out of my hand, with the stock boot-grips on. I'd suggest, first, that you try and find some 125 gr. ammo to shoot out of it. In a real standard pressure round, at least for me, this lighter bullet brings the level of recoil down to where it's really fun to shoot.
On the other hand, I got the .357 capable gun because I wanted to be able to shoot .357, and that I did for the first time today. I mail ordered two kinds of 'light' .357 from an internet store; the Remington Golden Saber and Proload's Tactical Light. Both are 125 gr. JHP, with well-designed bullets, and both hit around 1200 fps out of a 4" barrel--so, conservatively, 1100 out of a snub. Now these, I would not want to shoot 50 of in one session. Nor was I tempted, after a couple cylinders of each of these (and even apart from the ridiculous expense of 'em) to try any of the full-on 158 gr. .357s I had along for my L-frame. BUT, they can be shot, and accurately, and with the stock grips. Which brings us to your original question.
If I did not absolutely know I wanted to be able to comfortably carry this gun in my pocket, I would not have paid the premium for it. For any other mode of carry, for anyone who wants a .357, I think a heavier gun makes more sense. So, because pocket carry is the raison d'etre of this gun, I'm going to leave the stock grips on it, 'cause they're the smallest thing going--even though cleaning it after today's session will include cleaning a little blood off the backstrap. Now, I couldn't do this if I belonged to the 'practice with what you carry' school of thought. I like to shoot, and there's just no way I could afford to shoot that much of any premium ammo, which is the only thing good enough for carry IMHO. And, while I can take a little bit of punishment for the sake of competence, I'm not going to be shooting .357 by the crateload. I'm going to keep shooting a bunch of those easy-going 125 gr. standard velocity shells for fun and training, and then a cylinder of the premium stuff I plan to pack (probably the Pro-load; it was right on POA for my gun).
If the compact, lightweight and powerful package of the 340 appeals to you, then I just don't think it makes sense to bulk it up and defeat its prime virtues with bigger grips. But then, if you or your wife are sure you don't want to shoot .357s out of it as is (I know I'd never encourage my wife to shoot a .357 out of this thing), why not get a model 342, which is limited to .38 special? Jeez, that's a lot of writing, and I hope it isn't all unwelcome--but good luck at any rate with your decision.
cw
