IMHO, "it depends". I agree with Dr.1 that you should try to keep 100% or a little above that on the EPA on high rates, otherwise you are throwing away servo resolution. However, there are cases where it's more useful to dial down the EPA and not sweat the resolution. (like in some installations, where the sideways movement of the pushrod at the extreme ends of travel get in the way and don't add much throw anyway).

I only use dual rates if I want to change throws in flight. Most of my planes don't have them set, since I normally don't need rate changes. Otherwise I use mechanical setup and EPA.