If you have your own private bulls eye competition going on consistency is everything. Whichever you pick stay with that one.
Also I have read S&W revolvers are factory 'aimed' for 158 gr bullets at 25 yds.
As far as 'kick,' typically a 357 caliber bullet is exiting your revolver a LOT faster than the 38 cal, it is a matter of physics - For every action there is an equal and opposite reaction (recoil). The same size bullet traveling 50% or more faster through the same barrel will cause more recoil. 'Felt' recoil can be increased or decreased with longer or shorter barrels, bigger or smaller weight guns, hotter loads and reduced powder loads, etc. The calculation for bullet 'energy' includes squaring the velocity, so recoil goes up much more by adding speed to a bullet; adding a bit of weight - 158gr vs. 125gr - to the bullet and not changing the speed (or even slightly reducing it) means the recoil is not changed as much.
I don't have an 'N' frame, but I do have a K frame 4" and a J frame Airweight, the 'kick' from the 357 in the 4" K frame is heartier than the kick from a 38 in the 1 7/8" J frame; but when I add +P loads to the J frame the felt recoil is not much different from the 357 K frame. Contrary-wise, when I shoot regular 38 spl through the K frame the kick is negligible, and easy on these old hands.
I practice defensive shooting, hitting a paper plate at 3-8 yards from different positions is good for me. But if I was to shoot bulls eye for recreation I think I would buy a big box of 38 158gr at the best price and shoot them out of both J frame and my K frame. I could shoot 38's all day that way.
Whatever you do, do it consistently. Find a brand and size bullets you like and stick to them. That way hitting the bulls eye well is your responsibility, not the bullets.
HTH
