Originally Posted by BGM

In some aspects, 20s will not perform better than the 19s because of weight but not in terms of stopping feet and skidpad tests (below). Stopping feet is an every day driving occurrence and so is handling (skidpad more related to higher speeds).

Car and Driver:

X5 non-20s:
Braking, 70-0 mph: 169 ft
Roadholding, 200-ft-dia skidpad: 0.82-g

X5 20s:
Braking, 70-0 mph: 159 ft
Roadholding, 200-ft-dia skidpad:: 0.87-g