I will most certainly give you kudos for coming into a G37 forum and ask us all. You knew the answers you were going to get from us, and my opinion certainly is no different. I also researched cars before I bought my G, and my research started differently, but that is a long story...which I will save for some
other long reply.
I know you are comparing an Audi to the G37, so I will stay on task. If you want an all-wheel drive car, which since you are a current Audi owner I will
assume that is something that is likely an important selling point. Simply, I love my G37xS! Because it is a rear wheel drive car, unless I choose it to be in all-wheel drive mode,
OR if it senses slippage in snow or rain (or even in a quick start!

). I love the fact that this car is a rear drive car when I want it to be. It gives you the handling of a true sports car (a la BMW, corvette, etc.), but when you need it, it is an all-wheel drive car. AND it handles quite well in the slippery stuff. I have put 15K miles on my car in less than a year, and the only complaint I have is that the OE tires are not going to last all that long (maye 5K more miles)....but, summer's coming so it all should be fine here in Colorado. I also own an Expedition, and I have no worries about bringing out the G in a snowstorm...in fact it's kinda fun to piss off the truck & SUV owners in the shiiity weather!
In summary, do your research, but mainly do what feels right to you. Again, thanks for asking all of us Infiniti owners what we think. Hope it has been helpful, as well as informative. Good luck in your venture.
CJS