If you're comparing the 1 to the 3 E9X generation, both x28i?
I think the 1 with a manual is almost 200 lbs lighter than a 3. I would think it's a little quicker than the 3. The 1 wasn't here in the US when I bought my 3; think I would have leaned toward the 1 if it existed at the time.
If you tend towards practicality, the 3 sedan is a better choice. If you tend towards total driving experience and want a coupe, perhaps the 1 has an edge, but you will probably enjoy either.