I have shot both, but prefer neither. I recommend the Ruger SP101 with the 2.25” barrel. The longer barrel will produce greater velocity and energy for both .38spl and .357. Although the SP101 is slightly larger and heavier than the LCR and M&P (i.e., 1/2” longer and 8.9oz heavier than the LCR), it is still a very concealable weapon depending upon your body type. I carry mine inside the waistband with a loose shirt (tails out) or outside the waiseband with a sports jacket, vest, fleece, or sweatshirt. It also conseals well in the front pocket of my cargo pants/shorts and chinos.
Lastly, while the SP101 still has a respectable kick with .357s, it is a lot more manageable than the lighter/smaller LCR and M&P, even with the OEM plastic grip. With that said, I wear a leather “weighlifting glove” when I practice at the range.
The very worst thing that can happen is that a single American own a gun! THIS IS AWFUL! We need to ban guns, steel, lead, chemicals, schematics, manufacturing machines, hands, and people, because all these things result in guns. If you shoot at the sun with a .45 caliber, you will put it out. If you shoot into space, you will invariably hit an alien planet causing an interstellar war. Bacteria and germs can settle on guns, making them horrible sources of disease.