Well OP, I think you've pretty much heard it all from here. As a couple of other people here have said, if you are feeling the ZL1 more than the 370Z, then go for it man. Personally I wouldn't let a few other peoples' opinions change my mind if that is all they are. But if you truly are still up in the air about it, think about what you've got, and what you're getting.
One advantage I can see to the ZL1 is that you will have a back seat to throw the kids in. Granted, they most likely will not want to be there past the age of 10, due to lack of space, but at least they will be around for the thrill.
Me personally, I think I'll be biding my time before I get another toy. I hear that Chrysler is thinking about taking the mid-sized car in their line-up (Avenger, 200C) and making it rear-wheel drive. And they have developed a new Hemi, a 6.2L Supercharged V8 that is looking at over 600hp and around 640ft. lbs of torque, which they may drop into said mid-sized rear-wheel drive car. If that all proves to be true, that little beast will truly be a terror, most likely eating a ZL1 for lunch. It's all speculation though, and probably will not happen for a couple of years yet. (
News: Barracuda dead, Avenger reborn?)
You may have noticed that I like Chryslers as well as Nissans...
All that aside, a lot of people like the retro look with the new pony cars, and Camaros are definitely enjoying a lot of time in the light. In the end, it sounds like it's just going to be a toy, so at least go with the toy that you like most.
Good luck chief!