Ahhhh... I think the GTS-t will be less susceptible to changes in turbo setup, and because they're so quick to spool up anyway, a small gain or loss in turbo boost threshold will have minimal effect.
The GTR, with it's entirely too laggy standard setup would definitely be less driveable as a street car with even 500-1000rpm more lag from a bad turbo choice. Fine for track, but a 5000rpm boost threshold doesn't make a street-friendly car IMHO.