What's the difference between the Steam version and the Windows Store version?

The Windows Store version and the Windows Phone versions are cross compatible, which means the Windows Store version supports mobile interfaces such as touch screen and tilt.  Gamepad is supported on Steam and on Windows Store versions, but not on the Windows Phone version. 

The Steam version includes all the online stuff, with synchronous multiplayer, VR Challenge ghost racing etc.  The version that is in the Windows Store has VR Challenge but no online multiplayer. 

The graphics and performance are similar on Steam PC and Windows Store.  The Windows Phone performance of course would probably be less.