I own a Hellcat. It's easy to do the math and see that with 640hp, the ZL1 is going to be faster. Better power to weight ratio, more tire out back, more sophisticated launch control.Let's see... Ride in a ZL1 that sounds good while trying to see the tail lights of the GT500 and Hellcat that just obliterated you... Yeah, makes sense.
As far as the GT500 being faster than the ZL1 if it has the V6, color me skeptical. In the GT they're promising "more than 600 horsepower" but haven't gotten more specific. If it has roughly the same power as the ZL1, it still won't be as fast because the new Camaro has a significant weight advantage over the Mustang. But until we know how much power both cars have, it's all guesswork.
It's not just the V6, it's also turbocharging. Have you ever heard a turbo motor that sounded as good as an NA or supercharged motor? I haven't. Have you seen the videos of the full race trim GT going around the track? If you like super loud whoopee cushions, it's perfect.As for sound... If sound and two cylinders are the only reasons you wish to take a ZL1 over a TTV6 GT500, then I don't think there's much to tell you.
But I'll be the first to admit that the sound of a car is more important to me than it is for many other enthusiasts. Like, if a new Tesla came out that blew the doors off of both the ZL1 and GT500, I wouldn't buy it. The sound a car makes is a big part of the emotional satisfaction for me. Don't take it personally, we just don't all like the same stuff. I can easily see buying a GT500 if it's configured a certain way but I can just as easily see taking a pass. Time will tell.