FWIW, I owned a G35X 5spd and was given a G37X 7spd as a loaner. I could not tell one bit of difference, except the tranny of course. I really dont think the extra 25hp is worth the cost of buying a new car, personally.
Even if buying new, I would take the better deal on the "older" leftover FX35s and put the cash i saved into a good exhaust and intake, probbaly pick up that missing 25hp and sound way cooler while you're at it.
As far as resale, well, the FX37 will definitely have better resale, unfortunatley, becuase the 35 will be "discontinued" :/