Hi Deane.
They are not 100% the same but use many similar features. The MidJay Pro is a general multimedia module which can be used as an arranger but also leans towards other entertainment uses (eg singers or guitarists)
The MidJay Pro can be run with a controller keyboard and confoms to general midi standards, however not all functions will be easily available. In my oppinion it is far easier to use the excellent touch screen on the MidJay Pro than any other keyboard control system currently on the market.
Both SD7 and MidJay Pro use KST format, but a converter is installed. A video can be found here:
https://www.facebook.com/ketron.uk