EPR is a linear indication of thrust.
RPM is not.
.1 epr anywhere on the guage is the same amount of the thrust (devide rated thrust into MAX Epr and you get a good idea)
N1 however as a measure of thrust is very poor. It moves all over the place depending on temperature and rotational speed. To go from 40 percent N1 to 50 Percent N1 may be an increase of a 1000 lbs of thrust. but go from 97 to 98 might be 10,000 lbs of thrust depending on the engine and application.
Furthermore, if you have an engine that is flat rated in thrust below and certain temperature (Virtually all of them are) the RPM that correspondes to that rated thrust will decrease with temperature. So you can overpressure the crap out of the engine and its mounts while still well below the rotational limits of the engine. The same EPR however will equal the same thrust regardless of temperature.
HOWEVER, this whole arguement falls apart once you leave sea level..
Cheers
WIno