What are some alternatives?
When comparing VR Sketch and Quill by Story Studio, you can also consider the following products
Tilt Brush by Google - Paint in spaces around you with Virtual Reality
A-Painter - Paint in VR in your Browser
MasterpieceVR - Powerful VR sculpting & painting tool
Kingspray Graffiti - Collaborative graffiti simulator with realistic spray and drip effects.
SprayPrinter - Convert digital designs into wall art from your smartphone
Oculus Medium - Sculpt, model and paint in virtual reality on a 3D canvas.