There isn't really any benefit. The E28 535i/S ones cost about 60% less than the M42 ones, but that's about it.
Stiffer motor mounts combined with the M42, which runs rough for a 4 cylinder, will transmit a ton of noise & vibration into the cabin. I rode with them for 4 years, and when I finally shelled out the cash for M42 mounts I couldn't believe the difference. It was like a new car.
So, stick with M42 mounts, unless this is a track only car. There is a slight improvement in throttle response, but not nearly enough of one to justify the noise & vib in a street car.