Well I didn't had a chance to drive 125i but my sister owns 325ti (compact) which should be something similar to 125i short wheel base great balanced weight nice NA engine + perfect sound. And the feeling of GO CART.
What I'm trying to say real balance is behind 125i weight distribution and stuff like that.
Just look how many problems have OEM 135i although it's a great car. But as we say it should came from the factory with Performance suspension, w/o runflats, with M3 bushings etc....