Fishnets are used mostly as a sort of undergarment, it defines curves by sticking close to the body, generally making the wearer look more muscularly defined. It is also related in dance wear especially for ballroom, theater jazz, and showgirl numbers. Some fishnets are designed by famous fashion icon such as Polo Ralph Lauren.
Lightweight Fishnet Pantyhose: It has a lightly softer feel at first touch than the medium weight stockings, and are quite soft on the legs. When dancing, as the legs slide together, the feel is light and smooth. The waist is a comfortably soft elastic band with just enough texture to stay in place. As with most tights or pantyhose, it takes a bit of adjusting the seam around the foot to place it in a comfortable position.
Medium Weight Fishnet Pantyhose: The fabric for this pair is a little tougher at first touch. With the durable, more coarse fabric, they might tend to shift on the legs less with movement - they seem to stay put with just a tiny bit more grip. When the legs and knees come together, the friction of the netting sliding against itself can be felt more distinctly than in the other pair.
When in need of fishnets, there may be a few differences, but as mentioned above - it’s all a matter of personal preference and choice.