What are some alternatives?
When comparing VR Sketch and A-Painter, you can also consider the following products
Tilt Brush by Google - Paint in spaces around you with Virtual Reality
MasterpieceVR - Powerful VR sculpting & painting tool
SprayPrinter - Convert digital designs into wall art from your smartphone
Poly by Google - Explore the world of 3D
Oculus Medium - Sculpt, model and paint in virtual reality on a 3D canvas.
Sketchfab Download API - A search bar for the 3D world