I have gone for the 3D connexion CADMouse and Spacemouse Wireless. Love this combo. I would love the Spacemouse Pro but funds did not permit. I have mapped the two space mouse buttons to different things but in Solidworks/ PRO E its 'normal to' view and 'delete' - my two common keyboard presses. For the CADMouse the middle click the two forward and back buttons toggle my planes and sketches hidden or shown.
The CADmouse is actually really chunky so your hand really does encompass it, I rarely get any sort of ache. With the spacemouse combo there is a lot less movement on the mouse, as the other hand does all of the rotation of the model. So it is shared.
Another tip for RSI avoidance is to turn whatever mouse you owns sensitivity to full, it takes a little time to get used to it but there is less wrist movement overall doing the same tasks.