The rigidity would be better if you had a bigger machine with more heft.
The 0XA is the size that a 7" should have. You may think the AXA will give you more rigidity, But more rigidity starts at the machine, not the holder. The holder (no matter what size) should lock up tight, the slideways are where rigidity is lost, so having loose, or light duty slideways will defeat any supposed gains , which I don't think you will get.