The GS-R head will give you slightly more compresion.
The B16 head and ITR head are very similar except for the ITR head having a mild port and polish and valvetrain upgrades.
Here's the problem. If you get a GS-R head, you need a GS-R I/M and GS-R Intake. If you get a B16/ITR head you can either use the B16 I/M or the ITR I/M. Same with intake.
Also, the GS-R I/M has what they call "secondaries." Which is another "door" that opens in the I/M. The B16/ITR don't. You can clear that out of the GS-R I/M and have it flow a little better.