So I ended up driving both a 2015 Mustang GT and a 2015 Challenger Scat Pack 392 the other day...
For being big and heavy the freakin Challenger hauls ass! The auto shifts so fast. The interior is super nice, really driver oriented like a C7 is. That 392 pins you in the seat without problem at all.
The Mustang was nice too, but the one I drove was a base interior auto so it wasn't as nice inside. It's a 2 seat car, lets be honest..the back seats are a joke, but it felt nice and the 5.0 has a great exhaust note, just the exhaust itself is really really quiet.
I would be happy with either one, honestly. The advancements in design and interior quality have been amazing over the last few years...
Now I just have to go find myself a 2015 SS to drive to be fair..gotta be fair ya know