The heavier bullet in ammunition will deliver a slightly stronger recoil impulse in this lightweight compact pistol.
It takes a good recoil impulse to overcome the initial resistance the Shield's compound recoil spring presents to the gun. This is the design, and it does loosen a bit as the gun wears in.
Why not try shooting the gun with both weights of ammunition. Use the standard velocity versions in 115gn and 124gn and see if you have any difficulty controlling them.
It's well worth your time and the small expense to attend a NRA Basic Pistol class... You'll learn the basic principles of shooting, safety and more details about how firearms work and the technology behind them. Look for an area gun club with a volunteer instructor team.