You cannot compare these two cars. If they made an RS4 coupe, then you could compare the M3 to that.
Just because Audi chose to make their version of the 335i limited production and call it the S4/S5, doesn't mean it is their M3 equivalent vehicle.
Whoever said the S5 is faster on the track is an idiot. I could pass Mario Andretti in an S5 any day of the week.