123 step to developing questions - indiv project

1 - Sushi has varying levels of quality.
2 - Why is it that pretty much any restaurant or store you buy sushi at will have its own flavor and qualities? There is a lot of variability and there must be something that sets one type of sushi apart from another.
3 - Further investigation will allow me to see what components are involved in making sushi and I can better determine aspects that will cause one sushi to be a better quality than another and vice versa. It should be easier to rate the quality of the sushi in order to categorize the varying levels of sushi.

Questions:
What is it that differentiates the level of quality among sushi? Some are good and others are not so good. Is it the preparation techniques? Is it the type of materials and fish used? Does geographic region play a role? What about the tools and type of knife used?