Every Type-R head is ported from the factory, hence the use of a PR3 casting as a starting block. The PR3 has more surface area to work with when porting than the P72 (GSR).

If you're not going to port either head, the P72 will give you a tad higher CR and flow numbers. However you pretty much have to buy a new intake manifold since any ECU you put into a CRX won't know what to do about the secondary runners on the stock GSR piece.

On the original subject:

The dyno of which you speak was posted to show the lameness of Spoon products. That's a B18C5 which put down 175 to the wheels as opposed to around 165 in stock form. I've seen properly built B16's lay down numbers in the 190's so there's not too much cause for concern.