I to traded from a 2010 r/t 6spd (14 months and 14,000 miles to a 2010 srt 6spd. I can not say I feel any big difference at normal operating speeds in the engines. The 6.1 can be a bit more touchy in regards to fuel consumption but drive either hard and you are quickly approaching single digits. The best mpg hwy I had on the R/T was 25mpg and the SRT is 24 mpg (Trips over 150 miles). You can push the 6.1 a little further RPM wise and by seat of the pants (not very scientific) I think the power band is broader in the 6.1 at higher rpm. What I like about the SRT is the brakes and the "tighter" handling the car has (my R/T did not have the super track pack).