As an owner who recently purchased a GTR and pains more $ to get into a 2015 to avoid gearbox issues, only to have the gearbox go in 3weeks...I say youre likely buying a better car.
The new gearbox, assuming OEM, is going to better or equal than one without it, and not worse. The upside is newer, less miles on the clutch, and less fatigue in the gears.
In hindsight I wish I would have waited for a GTR w a Shep trans or got a 2012 and used the money saved on a new gearbox...gearboxes are expensive!