In response to your poll, I much prefer the R390 - it's much smoother than the GT1 to drive - especially with the stage 4 turbo on it.
The Nissan's pretty flexible with set-ups, as the basic chassis balance is very good - I've found lowering it right down, stiffening the springs (setting it slightly softer at the back compared to the rear), and then playing with the dampers to address under/over steer is pretty much all you need to do.