I have always wanted a 2001 911 Turbo. I make the money. I could own one. But I bought a Z. Why? Because a car is what you make it. I don't need or want a Porsche to take spirited runs through the woods. The Z, after only a couple of easy mods will do everything I want it too and then some. It will be difficult to even push it to its limit outside of the track. And I'm not even talking a Nismo. Just a plain 'ole touring base model. And hell, I've met guys that gave up far more expensive cars to get into a Z and never looked back. Don't think of it as if you owned a Z, it wouldn't be expensive enough or have the name stamped on it that would make you proud to own it. And I think that is the part that gets everyone.
In the end, it is what tugs at you more. If you have the means to own either, I would choose what draws you more. If not, everytime you pass one you'll say "Damn, I almost bought that!" Then you'll think of some BS reason to backup your decision to own one or the other that will make you sleep better at night.
I say get the Z. The Japanese can make some serious sports cars.
And besides! Why the hell would you get a Porsche before a GTR anyway?! You can get a 2010 for $65k!!!
Good luck with your decision. Hope whatever you get you will be proud and not look back.