Ahh horse hockey! I bought my 340PD not for the intention of shooting full boat Magnums but for shooting +p and +p+ .38's. It has nothing to do with overkill or a power trip and here's why;
The Scandium frames are stronger than any Airlite or Titanium frames therefor they can withstand the stronger pressures. Shooting Magnums in a 12oz gun is a waste, what small amount of performance gains you get over the .38 with a Magnum in a 1 and 7/8 bbl is utterly lost between harsh recoil, more muzzle flip, and a neat little tingling sensation going up and down your hands and forearms. At the most I might load up some .357 Mag Tactical lite's from Proload, a little better than a .38+P but still manageable and wont rip my arm off. One thing I thought was a great idea was posted here by Jim, load 4 charge holes with .38's and the last with a Magnum, by the time you get to round 5 it's your last ditch and you want to pack a wallop. Whether or not the stronger frame and versatility of going between ammo calls for the extra $150 dollar price tag of the Scandium is up to you and your wallet, but for some it's well worth it. Are there some who only see a 12oz Magnum and do not consider the downside or think logically about it? You bet, but those shooters will soon learn the benefits of studying up on guns they go and blow a fortune on as well as practice and training.
Just for the record I'd like to state that my next purchase will be a 386PD Scandium, I work security and I need a light gun for a shoulder holster to comfortably wear under a blazer. That gun will be shooting full boat .357's after working though .38', and .38+p's. At just under 18oz's it makes a lot more sense to carry in the Texas heat comfortably.
As far as J-frames having poor accuracy, bench rest that hot rod and see how much more accurate the gun is than you.