How to choose 2 flute and 4 flute End mill?

How to choose 2 flute and 4 flute End mill 

An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. End Mills are used for making shapes and holes in a workpiece during milling, profiling, contouring, slotting, counterboring, drilling and reaming applications. They are designed with cutting teeth on the face and edge of the body and can be used to cut a variety of materials in several directions.

Finishing End Mills are used in metalworking applications for removing material or burrs from a workpiece and leaving behind a smooth finish. 2 Flute Finishing End Mills are used for center cutting (plunge cut) operation and when chip removal in slots & grooves is a problem. Traditionally, end mills came in either a 2 flute or 4 flute option. Feed rates are slower, resulting in smaller chips, and allowing for the smaller flute valleys of a larger core tool. This also allows for more flutes to fit on the tool, which in turn increases productivity.

Four flute end mills are used for all end mill operations. The flute volume is less on 4 flute mills, but they are the most common number of flutes. The larger number of flutes allows for a faster feed rate. They may not perform as well in grooving operations, because the chips are crowded.