I love Zs. Ever since I saw my first 350z as a little kid I fell in love. I would say the exhaust note of the VQ engines are the same or if not nicer than the BMWs. 370s are my current favorite, however I've never put them in the same league as a BRZ or 3 series bimmer. There's around a 100hp difference between the Z and the other 2. The 370 could also be optioned with a limited slip, whereas the bmw you'd have to go M to get one. That would be very important if I were to track the car, which I'm contemplating doing. Maintenence costs would definitely be a lot cheaper then in the Z. Also as much as it would be nice to work on my own car, I do not want to be fixing something /replacing something every other week. Japanese alleviates the burden of that from my head. The bmw still is a great car, but now thinking about it more it would make more financial sense to go Japanese. The cash I would of spent on repairs, could be used on other things such as mods for the Z.
Insurance is probably a lot higher in a 370z then in the other two, especially me being a new driver. Still the 370 would be a hell of a car to drive.