something tells me the 1M would be just fine on the track....
But the right tool for the right job. Your Z4 isn't intended for heavy track use, and that includes everything from its suspension, brakes, engine mapping, gearing, steering, etc. It's compromised towards being a proper car for the road. All that these things highlight to me is how well balanced the M3 is between being a comfortable DD and a very capable car on the track. Short of a 911 or Cayman or CTS-V, there are few others that can compare in that respect.