I will muddy the waters a little more. The .38 spec. cartridge is 120 plus years old. The metals and merallurgy of revolvers of the early years(1900) are not as strong as todays revolvers. So they are more prone to wear and could have untold of rounds through them. The old guns were designed with 15,000 psi in mind. THEN later the +P ammo was made to increase the performance of .38 spec. So putting higher pressure ammo in an old revolver could expodentially cause wear and possible danger.
WC ammo was used almost exclusively as a target round. The WC bullets cut a very clean hole in the paper target. That made scoring hits close to the bullseye target rings easier. For target shooting the emphasis is accuracy not bullet velocity. There is no power factor in bullseye shooting. Bullseye shooting requires 5 shots in 10 seconds. So low recoil provides more time to recover and make a more accurate follow-up shot. Thus WC are low velocity and accurate target ammo.