Funny thing is.many who have an auto rave about a manual and some who have a manual wish for a auto especially if older driver.
In my personal experience manual tranny shifting becomes second nature after a while you barely notice you are still doing it.Also it does give better control of the car and results in better performance and they are also easier(=cheaper) to repair if ever need be.The 6 speed manual on this car is very well desigend by all accounts as well as mechanically very beefy with a lot of strength built -in
On the other hand if you drive mostly in city traffic the 5 speed auto tranny is as good as auto tranny's get.<and> the auto tranny in the G35 is the excat same one used in the much heavier Q45 with its 340hpV8, so you know that tranny will be extremly strong and durable in a G35.
If I was you I would spend a lot of time test driving both.Be suure you spend enough time drivign teh manual so u are comfortable with it to more accurately envisioon the driving feel you will have with it once you own the car.I would pick the manual, but in an enthusiast driven board like this one that will be more common, and teh g354 sutotranny certainly is a very good+strong tranny.
Fred...