My M3 is 19 and my wife's M3 is a 18. Definitely softer ride on the 18. I actually did a comparison on the ride back from the factory and confirmed that indeed the 18 has better efficiency by about 10%. I posted the details/results in another thread. The 19 are definitely sportier and you definitely feel the road. I am looking to add new springs on my 19. The 18in are perfect for in town driving. Hope this helps.I think 19s will handle better but 18s will give a less harsh ride, and a little longer range on the freeways