Tuning time is the same, for both PFC or nistune, both cars should be indistinguishable from each other drive wise, for track cars i would go pfc d-jetro on a street car i would recommend either PFC (normal) or nistune, nistune is great for passing epa (with all mods) and so far 400kw is about as far as ive pushed a GTR with nistune..
Atm there are some missing addresses in the nistune (all remap software actually) for GTR which are required to allow more control of IGN and INJ vs AIT compensation, once these addresses are found by Nistune or JWT etc i will use them in more hard tuned track style cars.
Based on the support we get from nistune i dont think it will take too long for the addresses to be found.
BTW im a nistune and PFC fanboy so if you go Nistune speak to your tuner and make sure the addresses for your particular requirements are accessible.
Like any ecu, correct application is more important than brand.