Depends on what you want. You want a car you can fix up and make fast? Go with the 350z. You can track that car all day long, and it will be cheap to fix.

I wouldn't even consider the Z4, horrid looks too many things going on with it. The front is rounded off, while the rest of the body is straight lines and sharp edges. Too me that doesn't compliment.

The Crossfire, is definitely a exclusive car. At least for now. More than likel you won't see more than one on the road at the same time, thats if you even see one everyday. I live in Houston where we have over 2 million people, only 3 times I've seen more than one at the same time. Build quality is superior to the 350z, not sure about the Z4. The downside of the Crossfire is its size, I would love the car to be a foot longer or so. I personally like coupes more for this car, it looks more aggressive and reminds me of classic Bugattis.

As for service work on your car, BMW is superior to all three of these cars. You will always get a loaner and they'll go the extra mile for you for service work. If the Chrysler had the service MB offers, no doubt go for the Chrysler. Warranty is longer for the BMW as well. So if you plan to buy and keep the car for over 3 years, thats something to consider too.