If I'm going to carry a .38 concealed, it ain't gonna be a 27 ounce one. My M85UL weighs 17 ounces and the airlites are even lighter. It's also +P rated.
My SP101 shoots about the same accuracy with .38 or.357, hard to discern any difference, both about 2.5"-3" groups at 25 yards and in my experience, that's about as good as I can shoot such a short sight radius. My Taurus shoots about 3" at 25 off a rest. I clean my revolvers and scrub the cylinders with a brush after every range session regardless of what I've fired in 'em. Cleaning is part of using. My mama taught me this about dishes and cooking and I guess it carried over to guns, but if I fire one round out of a firearm in the field, when I get home it gets cleaned.
A range, training gun, the .38 SP101 makes a lot of sense. But, for carry, I'll go airweight if I go .38 and save some pain. That Taurus is pocketable, the SP101 isn't, not in MY pocket anyway. It's just too heavy.
Recall that this revolver was originally designed as a .38 Special and that the Magnum chambering was offered by the factory only after one or more gunsmiths began reaming the chambers to accept 125 gr. Magnum loads.
IIRC, the frame had to be lengthened a tad so a longer cylinder could be fit in the .357s. The early ones were built on the .38 frame and labeled ".357 125 Grain" or something like that. A 158 wouldn't fit, protruded from the cylinder. I've fired 180 grain JHPs in my SP101.
So, is the current .38 SP101 on the newer .357 frame or do they still use the old .38 frame? If it's on the newer .357 frame, I fail to see how it could possibly be any more accurate, same freebore as in a .357 cylinder. Like I say, I can't tell if mine's any more accuate with .357 than .38, both seem about the same.