Borehole Drilling Methods - ​Percussion ​Drilling Method ​and Mud Rotary

Dear all, I have a question: what is the difference between the percussion drilling method and mud rotary? The contractor said he prefers using percussion method instead of rotary because the rotary method is unsuccessful in sandy aquifers!! He also said the rotary machine we cannot drill big diameter of a borehole (max diameter available in AFG 10’’) Also, the depth for the borehole should be between 80 and 100 meters and now the contractor is using the percussion method and he cant drill more than 65 meters. I will be hope anyone shares the answer with me. Thanks Eng. Mohamed el Sayed