A patented groove system consists of hardware and profile from a single supplier. Precision engineering ensures that parts are made to fit each other and that the degree of error is the smallest. When done well, air gaps are as small as a hairline gap. Parts are custom made and so, cost more than other common groove systems. Globally, there are only a handful of such suppliers, including Aluk and Schuco.
The normal groove window systems that you see in most homes are supplied by several suppliers using general parts. Window/door fabricators mix and match different parts using different types of materials. This usually means inconsistent quality and a poorer fit. This approach also has a higher degree of error and greater air gaps, leading to noises passing through.