Most bows, including Critter Gitters (I've had a few of them) will shoot a fairly wide range of arrows well, particularly woodies. If you strip the feathers off of them, you might find one that flies marginally better than the others. You might also just break them on the target. Most folks who shoot woodies don't bare shaft, they just find an arrow that shoots good and shoot it.
In my experience, you're usually a little better off if you overspine rather than underspine, i.e.,t he overspined arrow will be a little more forgiving, you can add a little more point weight without affecting arrow flight, etc., thus the 70-75 or 75-80 would be my choice. If I had to pick one of those, it would be the 70-75. Good luck.