Cube and Pico are similar devices - they both measure color (RGB, LAB etc), provide matches to popular color collections (RAL, Sherwin Williams + more) and allow you to create your own color collections to match against.
Some differences include: Cube can connect with a PC or Mac to provide a real-time link to Photoshop. At the moment Pico can't do this.
Cube has a larger sampling area than Pico, which can be more useful for textiles or other surfaces which need some level of 'smoothing' for accurate color capture.
Conversely, Pico's much smaller sampling area and overall profile makes it possible to measure small patches of color in tight spaces with a higher degree of accuracy. However, they both have unique software/apps that come with them.