The G37 is significantly improved over the G35, so I would say that if you are considering a G35, get one cheap. Don't buy an unsold new 2008 (if they exist), go for more like a 2007 and earlier. This will serve to insulate your cash against the significant depreciation that will occur as people want the G37 more and the G35 less.
Leasing is simple, to me. Never do it unless:
- You can claim it as a business expense
- You need/want/require a new car every 3 years and you drive 12,000 or fewer miles per year. In this case, leasing is actually cheaper than buying new cars and then selling or trading them in.
Also, I'm not a huge fan of the X. If you can do without AWD, get the regular G37 which will save you money and reduce vehicle weight, making it accelerate, brake and corner better. If you must have AWD due to winter weather, then consider other AWD performance sedans as well. For example, they aren't nearly as 'sexy' but you might think about a Subaru Legacy GT. They make about the same horsepower as a G35.