Wow, going out and buying a brand new car... I hate being poor
What are your plans with it? If you're planning to drift, I honestly recommend the 350.
I only have experience driving the RX8 (my brother had one for a while) but it's not exactly a great drift car. It's 50/50 weight balence makes it really neutral, but bloody spin happy in a slide.
I may not have driven the mustang, but I immediately know it's fall back. It's got a solid axil. I know that some of the best drifters drive with solid axils, but it doesn't change the fact that IRS is a superior design.
That leaves the 350z. Decent power, RWD, options for turboes and LSD's. what's not to love? There's actually a few problems I've read about drifting this vehicle. I guess it's known to understeer quite a bit. At least with a stock setup, coming into a corner breaking will induce pretty good understeer. I learned that from the 350z shock by Best Motering. Things might have been updated since, being as that video is like 4 years old but it was an issue.
Now do you want the advice you don't probably want to hear? I don't recommend getting any of these cars for drifting if you're new to the sport. As daily drivers, they'd be great. But as a drifter they will wreak havok on your wallet. If you want any of these cars go for it, but I truely recommend a cheaper older vehicle for drifting, especially if you're learning.
Even if it's just for a track racer, I would recommend something like a miata over these. I guarantee your driving will improve faster and in many ways, the vehicle will be faster than any of the suggestions above.