I see a number of forum posts asking the above question. What is quality, how can it be defined? Here is a brief overview of the different aspects of picking out a quality wood flooring product.
This can be difficult to ascertain but it is important to note that quality products start with quality raw materials. In engineered flooring, this pertains to the backing material (plywood for multiply products and wood fillets and backing veneers for 3ply products), the actual hardwood veneer, and the glues used to process the product into a piece of usable flooring.
How are the floors made? What type of equipment are they processed on? Flooring produced on high-end German machinery are more likely to have tight fitting tolerances and less over-wood (height differences) than product made on lower end machinery. Not to mention contractors will have less difficulty installing products that are easy to work with. That translates to less time they are working in your home.
Is the floor you are purchasing made in such a way that it can be expected to last a long time in your home? This pertains mostly to the thickness of the wear-layer on an engineered floor. Is there enough usable hardwood to be refinished multiple times so that a few years down the road you can have them re-sanded and finished rather than paying for removal and replacement of new flooring? There are other considerations but these are a few key items to explore when choosing a floor for your home.