I have a sage and absolutely love it, it has dominated my folding EDC needs since i got it.
At first glance the thing that stands out most to me is the difference in blade geometry between these two knives. The Sage is probably the best slicer i have ever used! Its FFG Leaf blade just slides through everything.
I don't have a Manix 2, but with its Saber grind and drop point, i would think it would have very different cutting characteristics. I would think this would make more of a difference than the blade steel here.
So i would say, it depends on the type of cutting you want to do with it. As people have said, the Manix is a sprint run, so buy it if you want it. I love my Sage I, and i wouldn't trade it for any sprint run (except maybe a better sage 1, hint hint).