Naming the most popular badminton strings is difficult because this depends on what your local stringers offers as it is impossible to stock every string. It also depends on where you are in the world as there can be culture influence.
In badminton there are basically three types of string, monofilament, multifilament and microfilament. Unlike tennis, badminton players tend to use the same type and gauge of string for the mains as well as the cross strings.
A monofilament string is basically a single core with a jacket or sleeve to protect it. The core provides the strength in the string. The choice of materials determines the strings stiffness and resiliency. The core is the source of the string’s power. Monofilaments tend to be stiff badminton strings and are generally used by beginners and intermediate players.
The jacket or sleeve coating protects the core. They have different textures on the surface which aid with control. A rougher surface provides more “bite” on the shuttle for spin and greater control.
A multifilament string has a different core. This is made from thousands of different thin fibres twisted together. These strings tend to have greater resilience and power.
There are also microfilament strings whereby the fibres in the core are even thinner than a multifilament. These strings are not particularly popular in badminton.