The Axiom is a stripped down version of the Pheonix. It has a generic camo and lacks disapator bars(the bars with pads that contact the front of the limbs) and only comes in a kit form. This coming year it will come with a polymer rail.
The Ibex, Pheonix and the Ibex are all functionally the same. If you are only hunting then the Axiom is perfect.
The Ibex is one inch shorter because of the stock.