The question is do you want to view CAD specific geometry, or just model for 3D?
VR is notoriously sensitive to framerates so if you want to create VR assets from scratch, modeling them in a typical animation package like Maya, Blender, 3D Studio would be most efficient.
If you want to go from CAD->VR, you will still need a conversion tool - going directly into Unity will not give you proper control over things like mesh normals or UV mapping which is important if you want to be able to shade or texture your model. If you just wanted to view solid colors for fun, that’s easier you an import an OBJ model directly.
Otherwise, export your CAD to any animation tool, Blender is free. You can use that to simplify and clean your geometry (delete internal polygons, objects, back faces to simplify geometry), create UV maps that match your intent, apply textures and then export to Unity. It’s important to know that textures and shaders are considered different in the game environment. You’d want to apply texture maps in the animation tool and then apply your shaders (material properties) in Unity.