Have you studied the course "Metal Cutting Principles and Tools"? This is explained in the textbook.

The greater the tip angle, the better the tip strength and heat dissipation, and the more suitable for heavy cutting. Moreover, the small deflection angle is relatively small, which is beneficial to improve the roughness of the machined surface.

D-type tool tip angle is relatively small, which can reduce the contact area between the tool tip and the workpiece during cutting, reduce the cutting force and help control the machining accuracy.

In addition, the angle of the C-shaped blade determines that it is suitable for both the outer circle of the car and the end face of the car, and has a wide range of uses. D type is suitable for finishing or semi-finishing excircle and digging a certain range of grooves, but it is not suitable for flat end face (only small depth cutting).

Generally speaking, Type C is widely used and everyone loves to use it. Similar to C-type, it is W-type (peach-type) with 6 points on both sides, but the angle is the same as C-type, which can reduce the cost.

My favorite knife is MCLNR, 95 main deflection angle, CNMG 1204XX blade.