The wieght saving of a wheel provides multiple benefits. As the wheel has a rotational acceleration component as well as in the direction of vehicle travel, a doubling of the vehicle acceleration improvement normaly associated with mass saving. Less gyroscopic effect allowing faster direction changes for the same input and then less unsprung mass with associated inertia and momentum to impact suspension control.
I was out bid on BST wheels and then bought OZ wheels. The OZ's made a noticable and beneficial difference I just reckon the BST's would have been more so and from what I hear, better than anything else you can bolt on.