Basically there are two types of edges, one is straight plain cutting edge and second is serrated edge. The serrated edge has micro serrations throughout the edge from beginning till end at the tip. Straight plane cutting edge is better in many ways, as it allows making fine cuts and since it is smooth, so it does not produced any sound during hair cutting. Straight plane edge is also useful for slice cutting (using slice hair cutting technique). However, despite of all the glory, the straight plane edge has its own limits.
Micro Serrated edge is more like a multi-purpose cutting edge. It provides many value added benefits. The most well known benefit of serrated edge is that it is simultaneously useful for both, dry hair cutting and wet hair cutting. It does not allow the hairs to slip or skip from its tiny micro teeth. Each hair that comes under the serration gets cuts immediately on the spot, even when the hairs are oily.
Micro Serrations also help to protect the edge from accidental damage due to contact with a hard surface. Imagine while hair cutting, your Scissors accidentally bump into the hair comb and the edge has a nick on it. This can be devastating. Whereas, the serrated cutting edge will tolerate such torture at significant level and will be as good as new.
Serrated edges are generally harder to sharpen than their plane bladed counterparts because it requires preciseness and experience in order follow the existing serrations and create new serrations over them. However, the serrated edge does not require re-sharpening more frequently.
The only negative view that has been recorded about serrated edge is that, it produces a minute sound while opening and closing the blades of a Scissors during cutting. This sound gets produced because of the very minor friction and air pressure generates, when the accompanying plane edge blade runs over the serrated edge.
No doubt that it is a necessity of a professional hairstylist to own at least one pair of Micro Serrated Scissors. It will not only contribute in his/her professional outlook, but will also give the versatility in the art of hair cutting.