Price/tuning/parts cost. Its basically the same car but $15-20K more expensive, only slightly better dif, tuning, and a somewhat better engine (much better heads/intake, but similar cube, junk pistons/rods, etc.). Interior and exterior are almost identical with only minor trim changes. Tuning as of today is $10-15K for anything beyond ~600whp (HP released BETA today for Gen4 but unproven as of yet, only affordable tuning solution is a generic mopar pcm), everything on the engine is noticeably more expensive as well to upgrade or replace. All the Gen4 interior and exterior swaps to a Gen3 as well if you like the colored interior and the Gen4 hood.
Justin