I use my GTR as a daily and apart from the maintenance & fuel costs I find it easy to live with. I haven't touched the engine in mine infact it still has the compliance cat installed and I think its quick enough as a daily. If you're going to get one as a daily make sure you aim your mods that way.
Stay away from big power that you will never use on the street. You can break every speed limit in 3rd gear and it comes up pretty quick even in a stock GTR. Get some decent suspension in there and a good flowing exhaust and away you go.
If your set on 300kw then I would go the GTR over the GTT simply because its easier to make the power and the power is more usable in a GTR. Have a look in the Forced Induction Turbo Stickys for some ideas for what turbos you will need and the supporting mods people have.
For 300kw I would be going for HKS GT- SS turbos or the Garrett equivalent. I think the 2860 -9s are the closest now. Or if you think you will be looking for more power later on go for some HKS 2530s or Garrett 2860 - 5s i think they are.