Which of the following is preferred for cutting ductile materials such as dentin?
Burs are generally preferred for cutting ductile materials such as dentin, whereas Diamonds are most efficient when used to cut brittle materials and are superior to burs for the removal of dental enamel.
Dental stones, especially diamonds, have the highest efficiency in removing enamel (brittle material), whereas carbide burs have the highest efficiency in removing dentin (elastic material). Removal of tooth structure using and stone should be confined to enamel and perhaps the superficial 0.5-1 mm.

Ref: Sturdevant's art and science of operative dentistry. 4th edition page 341
Operative dentistry modern theory and practice Marzouk page 77
Diamond burs
Carbide burs
Hand instruments
All of the above