Better is in the eye of the
Better is in the eye of the beholder & what you want in a car. Both are great cars. For a stock exhaust my 2014 SS Sedan has a meaner sounding start up & idle than my 2010 Challenger SRT8, 2012 Camaro SS/RS & 2013 Mustang GT. Full throttle goes to the SRT8 but they all have great sounding exhaust.
I haven't seen a 2015 Scat Pack yet but it's my understanding it will have the same exhaust as the SRT Core.