The rebound slide spring does two things:
1. It pushes the trigger forward after it's pulled.
2. It rebounds (rotates the hammer backwards after the revolver is fired) so that the hammer nose (firing pin) doesn't rest on a primer, and allows the hammer block to move into the "blocked" position.
The factory springs are designed to be ABSOLUTELY SURE that the lockwork will work as it should, and that the revolver will fire, even under the worst possible conditions. This results in a heavy double-action trigger pull, especially in the small J-frame revolvers that obviously have small and lighter weight lockwork parts. By changing out the factory springs and using lighter ones you can get a lighter trigger pull, but you may also get a combination of spring weights that fails to fire a cartridge during an emergency. If the lighter springs were TOTALLY RELIABLE Smith & Wesson (as well as other manufacturers) would use them.
Now the choice is up to you.