I haven't paid much attention to the new Challenger, so this thread kind of got me into doing some research - especially given that I'm rather bored right now....lol. So, I used the threads linked above to keep myself occupied for a while. To wit...
The quickest bone stock 392 Challenger I could find went 12.25 @ 113 mph
Source
The quickest bone stock 2010+ Camaro I could find went 12.43 @ 112 mph
Source
NOTE: This is a corrected ET, and while I am a "you ran what you ran" type of person, will use this ET in deference to the Forum on which I am posting.
The quickest bone stock 2011+ Mustang GT I could find went 12.22 @ 115 mph
Source
I also did average ET's (ya, quite bored). I couldn't find a "bone stock" Mustang 5.0 list, but if someone knows where one is, link it, and I'll do the math.
Average Challenger 392 ET based on above link: 12.76
Average Camaro SS link based on above link: 12.86
NOTE: About of third of the Camaro SS ETs were corrected, but like I explained above, I used them anyway.
I suspect the Mustang average is pretty close to both of those. In the end, their performance is pretty danged close, IMHO.