Pick what you want here, theres pro's and con's to both, do your research. Don't forget with RB it's .5-.6 more liters of displacement and with 6 cylinders you get the torque. The initial cost of an RB26 is more expensive at the beginning (not by much in my opinion), but you also get more power out of the box than an SR. Look at the cost of bringing an SR20 to the power and torque of a stock RB and you would be surprised.
I think this is a myth, I sourced my RB25DET complete for $2000, you just have to do your research and know what you're looking for and where to look.
RB Parts are easy to come by, so are SR for that matter. Anything imported is the same degree of difficulty of obtaining parts.
A lot goes the same for RB parts availability in the US, I've just learned where to source and cross reference parts to help me find US based parts that work on the RB.
One advantage to a 2JZ in my opinion are three things, US based parts, 3.0L vs. 2.6L, and the fact that the turbo sits on the passenger side, not interfering with the steering linkages or the heat from the turbo messing with your brake booster area.