The fifth gen have the E-Torque mild hybrid system. As far as I know, it CAN be optional on the Hemi, but don't think you can get the 3.6 with out it. The Gen 4.2 (Classics) don't get the E-Torque at all.
Also, as far as I know, MDS is still on the current Hemi. It's been on all truck Hemi's since around '08 (I think) with car Hemi's having it longer. At best MDS is good for around 10% mpg improvement, but only at constant speeds.
As far as engine management - I'm sure it's gotten incrementally better, but nothing outstanding.
Some of the changes in the interior are specific to the fifth gen, but most can be had in the Classics as well. As far as I've seen on the Ram ordering side, the larger screen/infotainment systems are available across the board.