Actually my 6.7 cruises at about 1400 RPM and revs to 1800 or so to climb a hill. To me there is a subjective difference between the 6.7 Cummins putting out 800 ft/lb of torque at 1700 RPM (58% of max) and a Hemi putting out 429 ft/lb of torque at 4000 RPM (67% of max). It is torque that accelerates the load not RPM and in that department the 6.7 wins hands down.