Fair enough: very often hardware gets picked simply because one of the
technical people has used it before - and nothing wrong with that!

The main reason for choosing the Cubieboard was the LVDS interface that can drive the Pixel Qi LCD without additional hardware. It has good community support, lots of interfaces (four accessible UARTS vs. one on the BBB, touch screen controller, etc.) and a suitable connector layout. This makes the adapterboard easier which is basically just power supply, RS232 level converters and a way of matching LCD and touch screen connectors.

Can you say if you're planning to support touch screens or if the plan is
to control the flight computer entirely from the control column? I can't
see any control switches in the photos of panels.

There are no control switches on the flight computer to keep size to a minimum. They could be easily implemented with a slightly bigger housing, but I really prefer the stick remote for in-flight use. For setup on the ground the touchscreen or a trackball is fine.

Michael