bigbuck--not sure if the figures you've got is on the ball.
Looks like you're talking about the 5575 arrows.
The GT 5575 XT Hunter arrows are 8.2 gpi and a straightness tolerance of +/- .003".
The Super Carbon Magum arrows 55/70 are 8.1 gpi with a +/- .003" S.T also.
What's the make/model of bow, the bow's DW, your draw length and the arrow length, this info will better assist in finding you the better of the two shafts.
However from what I have seen so far, you could be better off with the Gold Tip shaft.