Nanoleaf Light Panels and Shapes Triangles are both triangular in shape. Both are capable of displaying over 16 million colors. Both can react to sound. They are both controllable with the Nanoleaf app and other integrations such as by voice through Siri, Amazon Alexa and Google Assistant.
The Shapes Triangles are slightly smaller, lighter and thinner than the Nanoleaf Light Panels. Also, the Shapes Triangles have a larger illuminated surface area, whereas the Light Panels have larger and more angular dark corners.
For sound reactivity the Light Panels require an add-on Rhythm Module. This feature comes built into the controller for Shapes Triangles.
One of the biggest differences is that Shapes Triangles, along with the rest of the Shapes line are touch reactive, whereas the triangular Light Panels are not.
Also, Shapes Triangles and the entire Shapes line are designed with Connect+. This technology allows all the different Shapes to be connected together into one layout. Light Panels are not able to be connected with any other shapes.
One Shapes controller can control up to approximately 500 Shapes panels, but you will require additional power supplies as you significantly expand your layout (use this calculator to determine the number of panels your layout can support, and how many PSUs it will require).
The Nanoleaf Light Panels Controller can control AND power up to 30 Light Panels.