if you had both heads goin for the same price, then depending on what pistons are going to be used on youe setup than this is my opinion

GSR head if the pistons are going to be stock or up to 11.5:1 pistons, just to gain some comp. from the head

B16 Head if the pistons are going to be any higher comp pistons 12:1 and up. Honda mated the CTR pistons with that head for a reason, well the same head structure, difference was the CTR/ITR head flowed better because of factory upgrades., pnp, valves, IM, TB, cams,etc.