The math states that a R's itb flows as much as a 90mm tb. And you can bore an R out to 48mm easily, makeing it flow even more. People will argue which is better for a long time, but I think until someone actully sets up actully testing for the two, and not "my friend does better times now that..." but actully TESTS the two in a controled enviroment that it will be just an opinionated subject. Many think one big tb is better then quads... but there is normally a reason that big racers run some things, and if you notice, most of the supid fast race cars have itb.
You also need to look into the flow and gain. I know boring out the itb on an R gives you higher gains but drops your low end a little. Just food for thought.
Also food for thought, the RB26s came with itb and the responce from that engine is awsome. I think there was a reason that Nissan oppted for itb on the RB26 and the R, they were their turbo race engines. I think that in itself should say something for it.
But these area all just my opinions.