I do not own a Manix but I do own a Paramilitary and a MiniManix (slightly smaller than the Manix). Aside from the obvious differences, such as blade shape and handle geometry, I would say that their weight is probably the most dramatic difference. For its size, the Paramilitary feels rather light and this makes it well suited for an EDC. On the other hand, the MiniManix is quite hefty and you definitely know its there when it is clipped to your pocket. Its extra weight is due to its liners, back spacer, and large blade.
However, I believe that the MiniManix has superior ergonomics over the Para. It feels so comfortable in the hand and it is well suited for prolonged cutting. It feels good when gripped with or without the choil. Whereas the Para only feels comfortable to me when it is being gripped using the choil.