Dynamat & ERS do completely different things.
Dynamat is for vibration/heat/auditory reduction.
ERS is for EMI/RFI reduction.
Yes, the Dynamat will provide a slight bit of EMI/RFI shielding due to the 4mil Aluminum topsheet. But I'd guess that doesn't really do much as that's not what the Dynamat is designed for.
You might want to use both Dynamat Extreme & ERS. Put the Dynamat on first, then apply the ERS on top of the Dynamat.
But you really need to figure out what effect you want for wherever you're planning on adding either Dynamt and/or ERS and use what's best for that application.
