So both can create the same torque at the shoulder, but the dumbbell version may create more compressive and shear force inside the joint.
That does not mean dumbbells are bad.
Your joints adapt to compressive and shear forces all the time.
But in rehab, fatigue, irritation, or workload management, this difference can matter.
That is why cuffs or cables can sometimes be useful, they can keep muscular demand high while slightly reducing joint reaction force.
Important caveat: this is a simplified static model,Real life is more complex. Joint anatomy, tendons, ligaments, bursae, movement speed, resistance curve, and neuromuscular control all affect what happens inside the shoulder.
Practical takeaway:
For hypertrophy, dumbbells, cuffs, bands, and cables can all work well because each gives a different resistance profile.
For rehab, or injury management, cuffs/cables may help you keep the stimulus while reducing unnecessary joint stress ( this is based on an assumption and may not always apply, can be different for different types of injury and individual circumstances)
Not a perfect real-world model, but a useful way to think about exercise selection.
Disclaimer: This information is for educational purposes only