there are two b-series vtec heads, there is the pr3 and the p72

The PR3 comes on all VTEC B-series engines, minus the 3rd generation GS-R (though i do believe the JDM sir-g has the same P72 head as the 3rd gen)

the P72 is on the 94-01 GS-R, it has smaller combustion chambers and provides higher compression, it also gives better flow numbers than a p72, with the exception of a head that comes ported stock (such as the Type-R's PR-3)

in most cases the P72 is the more desireable head. it has the most potential and in most cases is already better than the PR3

in your case, the b17 head is a pr3, and the b18c1 head is a p72.