For what it's worth, I think in general the E90 was the same way. The 328 out braked and slalomed just slightly faster than the 335. I'm sure it's simply because of the weight. Sure would get 335 owners steaming hot on E90post when someone mentioned it. Hinting that their 335 wasn't vastly superior to the peasant-level 328 sure brought out some insecurities. And lots of entertainment for the rest if us
But as others have mentioned results will vary highly from test to test, so you'll never see "real" numbers. Tires: model, treadlife, temperature, etc.). Pavement: Just think of how highly variable each test surface can be between testing sites. Weather, car loading, fuel level (weight), etc.
I know in my E36 when I was running pure summer tires that braking was quite incredible. Noticeably less with narrower all seasons.
And again what was mentioned above, the bigger brakes will have to do more with brake fade, so expect those cars to have reduced fade on a track day. A single emergency stop on cold brakes - being light will probably be more beneficial.