The main difference between chop suey and chow mein is the style of the dish; chop suey contains meat and vegetables in a thickened sauce over rice whereas chow mein contains meat and vegetables in noodles. Chop suey is believed to have originated from Southern China in Toisan, where it was common practice to create meals from leftover ingredients. On the other hand, chow mein originated in Northern China and is based off of traditional Chinese food.
Chop suey means "mixed pieces," indicating the random variety of foods used in the dish, while chow mein means "fried noodles." Both of these Chinese dishes actually represent the cultures of Northern and Southern China. Whereas chop suey is served on rice, a popular staple in Southern China, chow mein's noodles represent the North, where rice is not a staple crop.
Despite their difference in geographical origin, it is interesting to note the similarities of the two dishes. Both dishes contain common ingredients such as beef, chicken, fish or shrimp accompanied by vegetables such as broccoli, cabbage, or green peppers. They also feature a grain: rice in chop suey and noodles in chow mein. Of the two dishes, chow mein is considered to be more authentic Chinese cuisine.