Here's how I look at the 1M vs M3 performance comparison (for what it's worth):
1M costs roughly 70% (30% discount) of the cost of an M3.
The 1M will provide approximately 85-100% of the performance of an M3 (depending on the performance measurement, ie, 0-60, skidpad, direction change, etc).
So, the 1M is an incredible deal for an M enthusiast, even a better "deal" than the M3. The M3 will still probably outperform the 1M, but you've got to pay for that extra performance.
Final observation. Assuming same driver, I would bet the 1M outperforms an M3 on a slower, tighter autocross course. The M3 would outperform on higher speed venues.