Owners who have driven both cars extensively tend to argue the Mercedes is at least as fast and more sophisticated, and note the 190E came first (the M3 was BMW's response). The recurring line is that the M3 wins on image and looks while the Cosworth wins for those who have actually driven one; several call the 16v the easier car to live with.
Which is the better car to drive: 16v vs E30 M3
Mercedes-Benz 190E 2.3-16 / 2.5-16 Cosworth (W201) · driving