Having owned both n/a 2JZ and n/a RB the power delivery is quite different. The 2jz has really good low / mid range power and torque and falls on it's face in higher rpms. The RB has good power all around the rev range and pulls hard all the way until red line. Both are going to be 180-200 hp and with a bunch more money 20-40 hp if your lucky. The 5 speed transmissions in the 2j's (from the is300 at least) have issues and just don't feel right, it's one thing I hated about my IS300. I personally like the RB motor over the 2J, it feels stronger, sounds better, and it's Nissan for god sake!
The question you have to ask yourself is what do you want out of the car? A track car? Sunday driver? No one here can tell you whats right for you. Do your research, make a game plan. Execute.