I am writing a technical specification for a product portfolio containing a series of related products, differentiated by quality, well, sort of. I am looking for a synonym of the term quality which best describes what I mean.
In everyday talk people tend to assign the term quality to how good a product is. For instance, an expensive high-end restaurant is of a higher quality than a fast-food place.
But formally in business, engineering and manufacturing, quality has a different meaning: it refers to the correspondence between the agreed and the delivered product. It's kind of related to the difference between the specifications (expectations) and the reality.
In this sense, a better restaurant does not necessarily have a higher quality. In fact, a fast-food could have a higher quality if it meets the expectations of a client better.
I am a bit confused, especially not being an English native speaker. How can I refer to as a better product? As much as quality is also an appropriate term here, I would like to avoid it because it's quite a technical and formal document conforming to the ISO 9000 terminology.
Back to my series of products, saying that one product has lower quality would not be correct. All products have high quality, but one is better than the other. What is the collective term for this?
An additional example: the iPad Air is a better product than the iPad 2 (screen, storage, etc.). But it is not of higher quality.