HI MoW.
I doubt that you will find many people on this forum that will throw rocks at the S&W 340PD, it's a superb pocket gun, especially with CT grips. In fact, many of us, myself included, are J-Frame fans as well as Rohrbaugh fans.
If a decision has to be made between the two, the decision may simply come down to what do you like best, or what do you shoot best, a wheelgun or an auto?
As far as convincing you, I don't want to do that, but I will mention that the Rohrbaugh is a little flatter in the pocket, and about 1" shorter. Also, I don't mean to be picky, but the 340PD is a 5 shot, while the Rohrbaugh is a SEVEN shot, with 6 in the mag. and one more already in the tube.
Honestly, both are great little guns, and personally, I think you should carry the Rohrbaugh in your right pocket and the Smith in your left pocket!
Whatever you decide, good shooting to you, and welcome to the forum!