Well, I drive like a manic sometimes, and what i like about the 124 is its size and manuverbility.
126 are very good, but if you need to squeeze into tight spaces at high speeds, then its not my choice. Its like giving a sniper a shotgun.
124 are newer designs compare to 126. but a later model 126 has more bugs worked out compared to a earlier 124.
Personally i like those newer or sportier looks. my 124 has clear blinkers, euro lights, s600 grille, etc. that makes it look sportier and more aggressive compared to a 126.
This is a opinionated question and i dont think there is a right answer, it just depends what you like and what your objectives are.
I like only one BMW, thats the 7 series. i just like the looks though. i have heard they are not reliable and have electrical problems. no offense to any bmw owner or afficianado, but in most peoples opinion a bmw is a step below a benz when it comes to class, presistge etc.