I use a trackball too, haven't owned a mouse since...ever?? works great with flight sims cause I just place it to the left of my flight stick and use my left hand to look around and right hand to fly.
But the 3dconnexions are a completely different device that you can pull, push, lift, rotate, & bend to manipulate objects in 3d space, it's design for CAD and 3d modeling but if it can work in conjunction with the TrackIR functionality in IL2 then you could use it like a trackball with 6DOF