Let me input here. I went with a Maxima and then bought another Z.
I like the Maxima better than the G37 Sedan. However, that AWD would be nice.
If you have a family the G37 makes more sense. If you don't have another sedan or truck in the family to do chores. However, you can always rent a truck for $20 at uhaul for the day.
If you don't need four seats all the time and your passengers don't mind the back seats of the G37S; I'd go that way. The couple of thousand you'll spend either way doesn't matter if you don't get what you really want.
In the end it's up to you. They are both great choices. In my case, I wouldn't trade my 370Z for either. I did look at the G37S and it's pretty nice if you need those extra 2 seats. But, in my opinion the Z still looks like a superexotic sports car and the G looks like Grandad's luxo sport tourer.
When I had my 350Z I also had a really nice used sedan for family duty. That worked out great. I've stepped it up a bit with the 2011 Maxima and 2011 Z and don't see any new cars for over 10 years now.
My last Nissan (Pathfinder 01) still looked and ran good after 10 years. I sold it for a upgrade that I could pull behind my motorhome. Nissan 4WD are not flat tow friendly ;-(
And remember .... all your base are belong to us ...
http://www.youtube.com/watch?v=8fvTxv46ano