i always chuckle a bit when people talk of power out of RB20, RB25 and in some cases RB30s.
10-12psi in a falcon nets some pretty farkn good results, but the same in one of the above motors - not so much.
but as tim said, they deliver power in a different way and the RB25 loves to be revved with some big cams in it.
the 4l puts out power vs boost almost on the same scale as a 2jz, so cant really compare the power output of the 2.
im sure the skyline would feel alot fast as you could probly drive it faster easier lol
if by some chance you need to replace the bottom end tim, put in an RB30e bottom end

with the RB25 head it will drop compression to turbo friendly and will be good for around 300rwkw.
cant complain when they cost $50 for a long engine lol