It all depends. Faster in the 1/8th mile, 1/4 mile, rolling start @ 30 or 60? The challenger is a heavier car, but has more tq. This means from a stop it will take off faster. However, my experience has been that a supra owns from a rolling start race.
If you're looking to see what you should build up, go with the supra. You'll make more power, more reliably, and get more street cred. Sorry challenger, I don't want to try to fix you after breaking you with 1200 hp. I'll take the supra any day.